Fixes wrong variable invoking during get transport

Now the method of transport() of queues/v1/client.py is invoking
wrong variable name. This patch fixes it and add an unit test.

NOTE: More unit test cases for v1/client.py will be added in a
separate patch.

Change-Id: I75a2498002bb2b9b7475bef0af5eebc8d82d662d
Closes-Bug: #1266467