Cleanup qvm_shutdown

[hippalectryon-0]

Mostly cleanup, with subtle inner API call changes that shouldn't affect users

Major changes

7d730eb harmonize behavior when has/hasnot_event

When have_events is False, after reaching timeout, the previous code calls Kill on the filtered current_vms = failed_domains(current_vms)current_vms = failed_domains(current_vms), whereas if it is True it calls Kill on all this_round_domains.

The commit harmonises this behavior to always filter.
This slightly changes the API calls, as seen in the modified utests.

a37814a cleanup dead code around args.wait

The current code does

  for vm in this_round_domains:
      try:
          vm.shutdown(force=force)
      except:
          if not args.wait:
              vm.log.error(...)  # THIS EXITS
          else:
              remaining_domains.add(vm)

From this point onward, if not args.wait, either we exited via error, or remaining_domains is empty (and then we return immediately after).
This makes most following code depending on args.wait obsolete.

Minor changes

7d730eb use a single asyncio interface for both cases where we do and don't have events

c08d6eb add utests

Note: this particular commit is mostly GenAI. Tests were reviewed manually.

[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.48%. Comparing base (c6b516d) to head (e59cad6).

Files with missing lines	Patch %	Lines
qubesadmin/tools/qvm_shutdown.py	93.75%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #448      +/-   ##
==========================================
+ Coverage   76.24%   76.48%   +0.23%     
==========================================
  Files          53       53              
  Lines        9325     9317       -8     
==========================================
+ Hits         7110     7126      +16     
+ Misses       2215     2191      -24     

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