Make sure we call BaseTestCase.setUp() first

Some test cases instantiate RPC clients in setUp() before calling to
super(). After we port to oslo.messaging, we'll initialize RPC layer in
BaseTestCase, so we should make sure we call there before proceeding
with clients in subclasses.

blueprint oslo-messaging

Change-Id: I6fdcba0ba690c75d1a472b3ad050c21f5f53a1d0
Merge "Make sure we call BaseTestCase.setUp() first"