agent, broker: handle manual migration of vm

If a vm is migrated manually, the broker will now detect this status,
propagate it to the agent, and the agent will switch state to monitor
the migration rather than simply waiting for a timeout due to bad vm
health.

Change-Id: Ic5024210e89a61d724bae191b8ccd913b78f1d31
Bug-Url: https://bugzilla.redhat.com/1026377
Signed-off-by: Greg Padgett <gpadgett@redhat.com>