Clean up testhack

Our setup_hack variables should override define- functions in the gateway,
so go ahead and copy into the object after construction is complete.

Change-Id: I0e7379836d3bacfb858b83d533c4f0fc83a68fa1
Tests for WorldPay order_id generation

Change-Id: I4002672421c3c72cb42f1f2509611bbfb13d6285
Merge "Clean up testhack"
Merge "Tests for WorldPay order_id generation"