gluster: Remove virt related mange event options for gluster only mode.

Currently "Add event notification" dialog for user Event Notifier
displays virt specific event options also for the gluster only
application mode.This patch hides virt related event options from
"Manage Events" for gluster only mode.

Change-Id: I7fec833cc9322ad0ee6cd5c48ee54fceafc00f21
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=973638
Signed-off-by: Timothy Asir <tjeyasin@redhat.com>