Fix pep8 issues

Apparently functional tests code caused oslo.config to try to parse cli
arguments. After that openstack/common/log.py tried to register cli opts,
but failed because cli opts can't be registered after cli args were parsed.

This patch moves config initialization to a separate method to prevent
cli args from being parsed on the load time

Change-Id: If40409b306a7aabdbd3cf467319a1574b440a690