gluster: Correct SWIFT status if no hosts in cluster

If there are no hosts available under a cluster the SWIFT status was
being displayed as Up. Corrected the same to show Unknown is no hosts
available under a cluster or removed all the hosts from the cluster.

Change-Id: I17080ac2d3eb5ec87b2efcc86bdca750995bce0e
Bug-Url: https://bugzilla.redhat.com/974560
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>