cli : enabling/disabling quota using volume set cmd deprecated

Using the command 'gluster volume set <volname> quota {on|off}'
doesn't really enable/disable quota. So, a message to the user is
provided. Message asks the user to use 'gluster volume
quota <volname> {enable|disable}' instead.

Change-Id: Ic4e12d5f8298ca9233639b4f6f8601ed6937fecb
BUG: 1024626
Signed-off-by: Anuradha <atalur@redhat.com>
Reviewed-on: http://review.gluster.org/6192
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>