webadmin : Rebalance status display bug correction

Due to NPE Rebalance status popup was displayed some times only.

This is now corrected.

Change-Id: I1116cf62df0aeffef26e91c7de63639d20f9b1d3
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1011778
Signed-off-by: Anmol Babu <anbabu@redhat.com>