Raise minimum oslo.log to 4.5.0
Raise minimum oslo.log to 4.5.0

The cinder/policies/base.py file makes reference to
versionutils.deprecated.XENA, so we need to make sure we're using
a release of oslo.log where that's available, which will be
any release containing change I6bf6997899f6c95e.

Change-Id: I292dc5fd764dae1a59f9d8f3d14c523aff92ca88

openstack/cinder,openstack/cinder,mahak/cinder,mahak/cinder