agent: don't crash on failed migrateStatus

A failed migration would trigger an unexpected failure within the agent.
Instead, catch the failure and process it appropriately.

Change-Id: I9da40599098446e6915a2bd675096d00fa07516d
Bug-Url: https://bugzilla.redhat.com/1026377
Signed-off-by: Greg Padgett <gpadgett@redhat.com>