Port cloudpipe extension to v2.1

This patch ports couldpipe extension from v2 to v2.1,
and have v2 unit test cases shared between v2.1 and v2.
Partially implements blueprint v2-on-v3-api

Change-Id: Id40c637c0fc207e97b1d094805eb0cee6e9cd9c9
Merge "Port cloudpipe extension to v2.1"