Handle existing security group rules in volume exercise

Change-Id: I0aa3bc0c6179f92a12c1e9bbace61597778ffa1f
Quantum FloodLight/BigSwitch Plugin Support

The patch introduces devstack support for the Quantum FloodLight/BigSwitch
RESTProxy Plugin.

Change-Id: I8c032fd16723ed6055821de0860fae508df371b7
Implements: blueprint quantum-floodlight-bigswitch-plugin-support
Merge "Handle existing security group rules in volume exercise"