Consider log_config deprecation since Havana

(See https://github.com/openstack/cinder/commit/1b3e4358715bad3c2309ac40785bd7c3b371284f)

Change-Id: I84f1b3ca6cd3cc5868029571f6e6d27999f9e15f
Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>