core: Disable unsupported fence agents in UI

Remove the alom Power Management agent from supported agent device since
fence_alom script was removed from the fence_agents rpm

Change-Id: I199d50968f42e1e237d8b2f26f1fda2c6407a061
Signed-off-by: Eli Mesika <emesika@redhat.com>
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=908278