Refactored the 'os security group rule create' command to use the
SDK when neutron is enabled, but continue to use the nova client
when nova network is enabled.
Added a release note for the change in security group rules output
due to Network v2.
Change-Id: I8c6c99d5272ff5d410a449f73d198d834c5cd96e
Partial-Bug: #1519512
Implements: blueprint neutron-client