Port SecurityGroupRules controller into v2.1

This patch port SecurityGroupRules 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: I23c6d7c70ec27068066e2a2e3c7764982bf8ed1d
Merge "Port SecurityGroupRules controller into v2.1"