Refactored the 'os security group rule list' command to use the
SDK when neutron is enabled, but continue to use the nova client
when nova network is enabled.
In addition, a release note was added to document the features
and fixes resulting from this refactor.
Change-Id: I24d04b720102ed1c60776e1ca67d4ca20e31b663
Partial-Bug: #1519512
Implements: blueprint neutron-client