[hyper-v] Invalidate cached mgmt IP address on update_state()

[xmkg]

The cached management IP address becomes stale on some operations when it happens out-of-band, like "multipass restart", where it's a SSH-induced guest reboot.

This patch fixes that by invalidating the cached IP address on every update_state() invocation.

Fixes: #3354

MULTI-2068

[ricab]

Many thanks for (re-)spotting and fixing this @xmkg!

The general idea makes sense to me, although in the long run I hope we can find a way to be alerted to ACPI events in the guest. I suspect it would be possible to subscribe over a VSOCK/SSH connection, otherwise we might use a heartbeat based approach.

I have a few requests inline, but I think we should let this one simmer in main for a while either way. It's been like this forever and the fix could have effects that we're not anticipating, so I wouldn't rush to release it now.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.44%. Comparing base (b144a59) to head (94212fa).
⚠️ Report is 60 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4207   +/-   ##
=======================================
  Coverage   89.44%   89.44%           
=======================================
  Files         260      260           
  Lines       15818    15818           
=======================================
  Hits        14149    14149           
  Misses       1669     1669           

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[Sploder12]

This is important for hostname resolution, is it done simmering?

[xmkg]

This is important for hostname resolution, is it done simmering?

@ricab ^^ WDYT? Should we include it in 1.17?

[ricab]

Yup, I am good with this, but I didn't test. @Sploder12 would you be willing to do that?

[Secondary review]

[Sploder12]

LGTM! Confirmed that running reboot inside of the VM via the Hyper-V interface (used passwd over shell first to make that possible) worked. Multipass picked up the new IP (once it was available)

[xmkg]

Great! @ricab, we already discussed this, but still want to confirm that you're on board with the idea of ignoring commit linter for older PR's and commits. If so, I'll go ahead and merge this.

[ricab]

Yes, it's fine. It's a transition period.