CBQE-1107: extend GetrTests from BaseTestCase

Change-Id: I03c3e071c39bf5823bd8ccd6c23f15eb9e07da9d
Reviewed-on: http://review.couchbase.org/25254
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>