API: return additional Hosted Engine information from vdsStats

Return additional hosted engine runtime information with vds statistics
which allows for better interoperability between the engine and hosted
engine agent.

Change-Id: Iaee2756d0652dc56439b8004e9260fcea927b708
Bug-Url: https://bugzilla.redhat.com/1053040
Signed-off-by: Greg Padgett <gpadgett@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/23263
Reviewed-by: Adam Litke <alitke@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/24090
Reviewed-by: Doron Fediuck <dfediuck@redhat.com>
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>