Make sure random tests have better chance of succeeding.

Change-Id: Iacc07dfd949ffaaacb64e68349580952c6c51df2
Reviewed-on: http://review.couchbase.org/29465
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>