mpr/mps: Fix a race in diagnostic reset

[imp]

Summary

There's a small race in freezing the simq when performing a diagnostic
reset. During this time, a transaction can slip through and encounter
the target id of 0. If we're still in diagnostic reset when we detect
this, don't say the device isn't there. Instead, freeze the queue and
return a requeue status, similar to what we do when we're resetting
a target and a transaction get here.

Sponsored by: Netflix

Test Plan

This race would be hit in about 1-2% of diagnostic rests, though some scenarios are more likely than others.
A heavily loaded system with a lsiutil induced diag reset would see it, but at a much lower rate.
Some IOC Fault-caused resets would set a hit rate of closer to 10%.

[mav]

Yes, unfortunately separation of SIM and queue locks created this race window.