oslo.log was added to global requirements, so we can migrate to this module.
Also we need this migration to be ensure that it works correctly with
log-improvements.
Since openstack.common.log is not dropped in oslo-incubator,
we shouldn't remove it.
Change-Id: I90468e4db812ae0b5d8a43a37206b236f8904661
Closes-bug: #1412673