Update sphinx extension logging
Update sphinx extension logging

Sphinx 1.6 deprecated using the application object to perform logging
and it will be removed in the upcoming 2.0 release. This updates our
extensions to use the recommended sphinx.util.logging instead.

Change-Id: I0b4d0d66ad60ff8e9b2d7de70d9858bd6ca5efa6
Signed-off-by: Sean McGinnis <961eeb09b6d45516665e15b82e013282c4faf575@gmail.com>

openstack/designate,openstack/designate,openstack/designate