net/http: TestTransportReading100Continue failures on `linux/ppc64`

[bcmills]

greplogs -l -e 'FAIL: TestTransportReading100Continue' --since=2022-01-01
2022-09-06T16:53:53-dc029f2/linux-ppc64-buildlet
2022-08-31T17:15:15-c708532/linux-ppc64-buildlet

(attn @golang/ppc64; CC @neild)

[pmur]

I suspect this is related to performance issues on the (old) ppc64 builder. I've been poking around the VM trying to figure out why everything seems to be running very slow.

[bcmills]

Maybe? But in both cases the test failed after 100ms or shorter. If the test depends on timing down to that level of granularity, I'd argue that it's a bug in the test.