Update azure instance state recognition

[djmitche]

https://bugzilla.mozilla.org/show_bug.cgi?id=1646061 shows an instance with powerStates ['ProvisioningState/creating'] which should probably be considered transitional. Also, it seems that vmInfo.provisioningState is redundant with the power states?

Now that we have registrationTimeout and reregistrationTimeout, the state recognition can be a little more conservative about killing instances -- if it misses an instance that has failed to start up, that instance's registrationTimeout will expire and it will be terminated anyway. And if it misses an instance that has failed after startup, reregistrationTimeout will expire and it will be terminated. So the worker scan's responsibilities are:

• in state REQUESTED
  • detect failed startup conditions and remove the worker
• in state RUNNING
  • detect instance stopping or deallocation and remove the worker

Since the documentation on lifecycles is next to useless, let's just look for known, observed situations, and treat everything else as OK (with debug logging for anything that's not known and observed to be good).

[djmitche]

Pete and I began pairing on this, and perhaps we can try again tomorrow. It will conflict with #3480, but we'll work that out..