CBQE-2131: Graceful Failover couchbase-cli tests

Change-Id: If234a84a08a5b14e89f646926995984c6b018425
Reviewed-on: http://review.couchbase.org/37042
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>