implemented faster certificate generation for cluster_run

and testrunner's make simple-test as a result

Change-Id: Ieb2627cd26be02e807a5007fe7621c8b18872c95
Reviewed-on: http://review.couchbase.org/35709
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>