webadmin: fix system-tree navigation for gluster volumes

Volumes with same name can be present in two different cluster.
So added cluster name also to the search string.

Also fixed the issue in selecting hosts part of gluster cluster.

Change-Id: I579bbe1f7b0a27cf0ee806554810a01a962cd71c
Bug-Url: https://bugzilla.redhat.com/973960
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>