connectivity log: report dropped devices

When a networking device is removed from the host it (and its most
recently recorded state) is logged to connectivity.log

Change-Id: I8ccb6b661efa12a7e7f3456caf23b15ea5c73ca5
Bug-Url: https://bugzilla.redhat.com/1111234
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30227
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>