CBQE-2419: update n1ql base64 clause tests

Change-Id: Ib7ceb904b8b8edc7deb67befeee7e32e1d9eab4a
Reviewed-on: http://review.couchbase.org/41777
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Tested-by: buildbot <build@couchbase.com>