This patch changes v3 attach_interface API to v2.1 and makes v2
unit tests share between v2 and v2.1.
The differences between v2 and v3 are described on the wiki page
https://wiki.openstack.org/wiki/NovaAPIv2tov3.
Partially implements blueprint v2-on-v3-api
Change-Id: If18676604edc8fea41d7888eb6546245163e91c2
Adds api sample tests and api samples for attach interfaces
Partially implements blueprint v3-api-unittests
Partially implements blueprint v3-api-specification
Change-Id: I54088cca1b83a8b92620062840606f2340a528c9
He Jie Xu