webadmin: New checkbox for volume delete permission under gluster.

This patch adds a checkbox for delete volume permission under gluster
which was missing before. Now permission to delete volume can be
added to a role by using this.

Change-Id: I576c940c628febf849442b7f52ecb498145ea1f9
Bug-url: https://bugzilla.redhat.com/show_bug.cgi?id=1015478
Signed-off-by: ndarshan <dnarayan@redhat.com>