Set vm state error when raising unexpected exception in live migrate

The instance stuck at migrating task_state when unexpected exception.
This is confuse for user, this patch set the vm_state to error.

Change-Id: Ib1b97452bc5e777c66c4d368f71156dbe1e116b7
Partial-Bug: 1397153
Merge "Set vm state error when raising unexpected exception in live migrate"