agent, broker: propagate engine status via shared metadata

Let each host find the status of its own engine (and vm) and propagate
it through the shared metadata, rather than each host attempting to
query the status over the network.

Change-Id: I791ae950db987c87679efb9c23ccb201895b20bc
Signed-off-by: Greg Padgett <gpadgett@redhat.com>