restapi: show host-id for a vm in an unknown state

When a VM was running in an unknown state, REST would not return the
current host-id for that VM.
Changed mapper to return host-id (and other dynamic info) as long
as the VM is not down for sure.

Change-Id: I8010522e42d1a7cfc963b2408b22c3bc468e30eb
Bug-Url: https://bugzilla.redhat.com/1144938
Signed-off-by: Eldan Shachar <eshachar@redhat.com>