webadmin: Hide Storage tab in gluster cluster

When a gluster only cluster is selected in the
System tree the Storage tab will be hidden.

Change-Id: Iae50b6a4769bd66261f4ac22f685bdc2a72cf2f6
Bug-Url: https://bugzilla.redhat.com/882095
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>