webadmin: Fix for NPE in remove brick status dialog

  Fixing the NPE in rebalance status dialog due to which
stop, commit, retain actions are disabled in remove brick
status.

Change-Id: Ibfe886c240a6d55798a1ad021c58dc874b8cff12
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1022511
Signed-off-by: Ramesh Nachimuthu <rnachimu@redhat.com>