This patch port SecurityGroup, ServerSecurityGroup and SecurityGroupAction
controller into v2.1 security_groups extension.
This patch just move the v2 code into v2.1 and share the unittest. The other
v2.1 related fix and improvement will be addressed by subsequent patchset.
Partially implements blueprint v2-on-v3-api
Change-Id: I93951ce677b74ebed7db1b2fff1f788344806dba