Change sleep time to be rampup_interval+run_time.   Change gateload.test to be 2 hours

Change-Id: If19efe2acbd63409e96b4d8ec31f6dc08450a898
Reviewed-on: http://review.couchbase.org/36799
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>