webadmin: hide add-brick force in unsupported clusters

'Allow bricks in root partition' option in
Add-Bricks popup will not be shown,
if the selected cluster doesn't support this.

Change-Id: I37d7e0d031b1e3933874b95d06b0cc1f89e95ab4
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>