Updated openstack/openstack
Project: openstack/oslo-incubator  b308be77f8a3d5c01e67d5467b38869d84bae5af

remove default=None for config options

In the cfg module default=None is set as the default value.

Change-Id: Ibb67da3b01c933b0789fd81f0b8a74e9aa30dd5a
Closes-Bug: #1323975