Removing initialized keyword from cluster search

The "initialized" keyword for Cluster search is no longer supported and
therefor was removed from the available search keywords for Cluster.

Change-Id: Ic3b1e7898ac488571162eeea24f1d45509099d9f
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1048735
Signed-off-by: Eli Mesika <emesika@redhat.com>