Add shutdown option to cleanup running periodic

Add a 'shutdown' option to the periodic task that cleans up instances
which are both deleted *and* running.

The option powers down instances and marks them as non-bootable.  This
is a flag for system administrators who would like to reclaim the
resources consumed by each instance, but leave the records around for
later examination/debugging.

DocImpact
Implements: blueprint cleanup-running-deleted-shutdown

Change-Id: Id95845eb995b62ed8858fe61c6fdb34045721674
Merge "Add shutdown option to cleanup running periodic"