`test_payment_path_scoring` is flaky

[tnull]

Just hit this randomly failing CI over at #4083:

test tests::test_payment_path_scoring ... FAILED

failures:

---- tests::test_payment_path_scoring stdout ----
node 0 TRACE [lightning_background_processor:1387]      Calling ChannelManager's timer_tick_occurred on startup
node 0 TRACE [lightning_background_processor:1389]      Rebroadcasting monitor's pending claims on startup
node 0 TRACE [lightning::ln::channelmanager:13496]      Handling event PaymentPathFailed { payment_id: None, payment_hash: 2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a, payment_failed_permanently: false, failure: OnPath { network_update: None }, path: Path { hops: [RouteHop { pubkey: PublicKey(2cc409776ac5704769641dfa01d00f5476617f031f0fe6964a67098247e9e55bbfb8078fbda6f6c993e1f8321eaae171e1cc261ec72cd5108bbf3d84c3885a03), node_features: [], short_channel_id: 4242, channel_features: [], fee_msat: 0, cltv_expiry_delta: 48, maybe_announced_channel: true }], blinded_tail: None }, short_channel_id: Some(4242), error_code: None, error_data: None, hold_times: [] }...
node 0 TRACE [lightning_background_processor:1372]      Persisting scorer after update
node 0 TRACE [lightning::ln::channelmanager:13496]      Done handling event, result: Ok(())
node 0 TRACE [lightning_background_processor:1472]      Persisting ChannelManager...
node 0 TRACE [lightning_background_processor:1479]      Done persisting ChannelManager.
node 0 TRACE [lightning_background_processor:1522]      Calling time_passed on scorer at startup
node 0 TRACE [lightning_background_processor:1532]      Calling time_passed and persisting scorer
node 0 TRACE [lightning_background_processor:1546]      Regenerating sweeper spends if necessary
node 0 TRACE [lightning_background_processor:1554]      Calling OnionMessageHandler's timer_tick_occurred
node 0 TRACE [lightning_background_processor:1560]      Calling PeerManager's timer_tick_occurred
node 0 TRACE [lightning_background_processor:1565]      Rebroadcasting monitor's pending claims
node 0 TRACE [lightning::ln::channelmanager:13496]      Handling event PaymentPathFailed { payment_id: None, payment_hash: 2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a, payment_failed_permanently: true, failure: OnPath { network_update: None }, path: Path { hops: [RouteHop { pubkey: PublicKey(2cc409776ac5704769641dfa01d00f5476617f031f0fe6964a67098247e9e55bbfb8078fbda6f6c993e1f8321eaae171e1cc261ec72cd5108bbf3d84c3885a03), node_features: [], short_channel_id: 4242, channel_features: [], fee_msat: 0, cltv_expiry_delta: 48, maybe_announced_channel: true }], blinded_tail: None }, short_channel_id: None, error_code: None, error_data: None, hold_times: [] }...
node 0 TRACE [lightning_background_processor:1372]      Persisting scorer after update
node 0 TRACE [lightning::ln::channelmanager:13496]      Done handling event, result: Ok(())
node 0 TRACE [lightning::ln::channelmanager:13496]      Handling event PaymentPathSuccessful { payment_id: 2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a, payment_hash: None, path: Path { hops: [RouteHop { pubkey: PublicKey(2cc409776ac5704769641dfa01d00f5476617f031f0fe6964a67098247e9e55bbfb8078fbda6f6c993e1f8321eaae171e1cc261ec72cd5108bbf3d84c3885a03), node_features: [], short_channel_id: 4242, channel_features: [], fee_msat: 0, cltv_expiry_delta: 48, maybe_announced_channel: true }], blinded_tail: None }, hold_times: [] }...
node 0 TRACE [lightning_background_processor:1372]      Persisting scorer after update
node 0 TRACE [lightning::ln::channelmanager:13496]      Done handling event, result: Ok(())
node 0 TRACE [lightning::ln::channelmanager:13496]      Handling event ProbeSuccessful { payment_id: 2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a, payment_hash: 2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a, path: Path { hops: [RouteHop { pubkey: PublicKey(2cc409776ac5704769641dfa01d00f5476617f031f0fe6964a67098247e9e55bbfb8078fbda6f6c993e1f8321eaae171e1cc261ec72cd5108bbf3d84c3885a03), node_features: [], short_channel_id: 4242, channel_features: [], fee_msat: 0, cltv_expiry_delta: 48, maybe_announced_channel: true }], blinded_tail: None } }...
node 0 TRACE [lightning_background_processor:1372]      Persisting scorer after update

thread 'tests::test_payment_path_scoring' (31928) panicked at lightning-background-processor/src/lib.rs:3311:9:
ProbeSuccessful not handled within deadline: Timeout
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/1bffa230015ba3c7826f6c5aceb0dc6e940d357e/library/std/src/panicking.rs:698:5
   1: core::panicking::panic_fmt
             at /rustc/1bffa230015ba3c7826f6c5aceb0dc6e940d357e/library/core/src/panicking.rs:75:14
   2: core::result::unwrap_failed
             at /rustc/1bffa230015ba3c7826f6c5aceb0dc6e940d357e/library/core/src/result.rs:1855:5
   3: core::result::Result<T,E>::expect
             at /rustc/1bffa230015ba3c7826f6c5aceb0dc6e940d357e/library/core/src/result.rs:1178:23
   4: lightning_background_processor::tests::test_payment_path_scoring
             at ./src/lib.rs:3259:25
   5: lightning_background_processor::tests::test_payment_path_scoring::{{closure}}
             at ./src/lib.rs:3281:32
   6: core::ops::function::FnOnce::call_once
             at /rustc/1bffa230015ba3c7826f6c5aceb0dc6e940d357e/library/core/src/ops/function.rs:250:5
   7: core::ops::function::FnOnce::call_once
             at /rustc/1bffa230015ba3c7826f6c5aceb0dc6e940d357e/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
node 0 TRACE [lightning::ln::channelmanager:13496]      Done handling event, result: Ok(())
node 0 TRACE [lightning_background_processor:1430]      Terminating background processor.


failures:
    tests::test_payment_path_scoring

test result: FAILED. 12 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 70.96s

error: test failed, to rerun pass `-p lightning-background-processor --lib`
Error: Process completed with exit code 101.