set up FakeLogger for root logger.

A recent change in openstack.common.log was made such that it
initialized the root logger instead of the project specific logger,
'nova' in this case.  Update the unit tests for this to fix the problem
where unit tests spam the console with log output.

Fix bug 1159978.

Change-Id: Id64a5b078b4024c3269086ed5d64940b3a38ddfa
Merge "set up FakeLogger for root logger."