Added ability to specify a prefix for testing.

Change-Id: I33964e420e862eee730dc2209af11e66d53f7b7e
Reviewed-on: http://review.couchbase.org/30098
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Brett Lawson <brett19@gmail.com>
Increased designdoc test timeout.

Change-Id: I7fe2355ff194e511539ec6986c303b4a67b692dd
Reviewed-on: http://review.couchbase.org/30099
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Brett Lawson <brett19@gmail.com>