Installation in networking-sfc

[Manik Sidana]

- [x] This doc is inaccurate in this way:
It should also mention about Pike and Queens as at first instance, it looks like SFC plugin is only available till Ocata.
- [x] This is a doc addition request.
- [x] I have a fix to the document that I can paste below including example:
Pike: latest <x.y.z> version
Queens: latest <x.y.z> version

If you have a troubleshooting or support issue, use the following resources:

 - Ask OpenStack: http://ask.openstack.org
 - The mailing list: http://lists.openstack.org
 - IRC: 'openstack' channel on Freenode

-----------------------------------
Release: on 2018-05-08 18:48
SHA: 379fcd5cfcb7a71e7dbbe969da0255bc3ff09a33
Source: https://git.openstack.org/cgit/openstack/networking-sfc/tree/doc/source/install/install.rst
URL: https://docs.openstack.org/networking-sfc/latest/install/install.html