client: API to retrieve local host score

Add client API to retrieve score of local host.

Part of a series of patches to enable maintenance mode for the HA hosts
and engine VM.

Change-Id: I49043a33e927393941e63a89e4e93519431f3695
Bug-Url: https://bugzilla.redhat.com/1015724
Signed-off-by: Greg Padgett <gpadgett@redhat.com>