CBQE-1682:expand cbtransfer tests coverage

Change-Id: Ic1c7bdcb03c046111d6ea44bd5f10917311cdc5f
Reviewed-on: http://review.couchbase.org/37716
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>