Updated openstack/openstack
Project: openstack/cinder  2bf82e893c1ab1db9f631cd191eaee7cd071ffd8

etc: replace NullHandler by Python one

We don't need to specify the NullHandler that was provided by Oslo
anymore, as Python 2.7 has this one. Let's use it directly.

Change-Id: I6948d1cd5a556779c1b1fd0a4161689e3a944b45