Add instance faults during live_migrate errors

When there is an error in the compute manager relating to
live-migrate, this change ensures that an instance fault is
recorded to help debug any issues.

We also need to look at better reporting of errors to users,
but this is not in the scope of this small change.

Change-Id: Ib4f0d0aea64468a4a1495b0318fc531a7d0d4eaa
Merge "Add instance faults during live_migrate errors"