Refactor security group rule delete to use SDK
Refactor security group rule delete to use SDK

Refactored the 'os security group rule delete' command to use the
SDK when neutron is enabled, but continue to use the nova client
when nova network is enabled.

This patch set also introduces new FakeSecurityGroupRule classes
for testing network and compute security group rules. And fixes
were made to the network FakeSecurityGroup class.

Change-Id: I8d0917925aa464e8255defae95a2a2adfb6cfb75
Partial-Bug: #1519512
Related-to: blueprint neutron-client

dtroyer/osc-lib