CBQE-0: try to identify problem when job hangs

http://qa.sc.couchbase.com/job/centos_x64--04_01--new_rebalance_mixed_cluster-P0/10/consoleFull

Change-Id: I0ddca51fce0fed9719e1d748947c02013fc45bb3
Reviewed-on: http://review.couchbase.org/30284
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>