CBST-3: reference testcfg module as cfg

Change-Id: Ic7c019a7903e377fc939adb531e8a0e6366acea0
Reviewed-on: http://review.couchbase.org/26916
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Tommie McAfee <tommie@couchbase.com>