Use debug level logging during unit tests

When unit tests fail we need to debug, so we should have debug level logging on.
We use fixtures FakeLogger during testing, to enable debug logging pass
in log level as a parameter.

http://bazaar.launchpad.net/~python-fixtures/python-fixtures/trunk/vi
ew/head:/lib/fixtures/_fixtures/logger.py#L68

Taken from nova (Change-Id: I70790aa39c0774726de71e5fa5751c45e7e34ffd)

Change-Id: I24bcce3a9a50322f20f06670d1fe95d929aa2e72
Merge "Use debug level logging during unit tests"