Catch NoValidHost exception during live-migration

To avoid leaving the instance state as MIGRATING if scheduling of
a target host fails, add this exception to the list of exceptions
for which the instance task state is reset to None.

Resolves bug 1166771.

Change-Id: I23343091725051624c0eb0b82e9f03a7f9d5f4f4
Merge "Catch NoValidHost exception during live-migration"
Add tenant/ user id to volume usage notifications

Volume usage notifications are generated to enable traffic based billing
on volumes. Include tenant id and user id to make these notifications
more useful to billing systems.

Fixes bug # 1158292

Change-Id: Ic71c10f0fc5d9e8c5a0e2f538de072e7ccca20ee