20457: Include delayed supervisor containers in overquota metric.

20457: Include delayed supervisor containers in overquota metric.

Previously, supervisor containers that had high enough priority to
run, but weren't scheduled because of SupervisorFraction, were not
counted in the containers_over_quota metric. This caused the
"overquota" metric to show a misleading time series as non-supervisor
containers made their way through the queue and the delayed supervisor
containers flapped between "not allocated because quota" (counted) and
"not allocated because SupervisorFraction" (not counted).

With this change, un-mappable supervisors always count toward the
containers_not_allocated_over_quota metric.

This also applies the "unlock if previously locked but now delayed due
to SupervisorFraction" logic to supervisor processes, which was
previously overlooked. This prevents supervisors from staying in
Locked state after being bumped by higher-priority containers.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curii.com>