CBQE-0: fix hostnamemgmt_tests.test_rename_with_warm_up

Change-Id: I3d9c41aeb40d685c940c8e707e2655259f20db40
Reviewed-on: http://review.couchbase.org/38233
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>