Support GlusterFS cinder backend

Commit 0971833 added support for multiple cinder backend types.
It initially only contains lvm and nfs. The following patch adds
glusterfs to the backends supported.

Change-Id: I9d5c1dfd4e0d05fcbfe3c35172150c57aa4e6eb2
Use the apache 2.4 ErrorLogFormat directive

Use the new ErrorLogFormat directive to make the Keystone logs
under Apache to look like the standard oslo log format.

Change-Id: Ie823abf2fa06b8ce22027c21bef455808a4a768e
Merge "Support GlusterFS cinder backend"
Merge "Use the apache 2.4 ErrorLogFormat directive"
Merge branch 'master' of https://github.com/openstack-dev/devstack