Documentation: pin the base distro release version

[OpenStack Infra]

https://review.openstack.org/319992
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/kolla" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 4044a3475e51f763f8d4f3feda003f0a4837f177
Author: Jeffrey Zhang <[e-mail]>
Date: Mon May 23 10:15:38 2016 +0800

    Pin the base distro release version

    Pin the base distro release version in the master branch(Newton).
    Only one distro version is supported. The supported versions are:

    * CentOS: 7
    * RedHat: 7
    * OracleLinux: 7
    * Debian: 8
    * Ubuntu: 14.04

    NOTE: Kolla will move to Ubuntu 16.04 in the Newton cycle

    DocImpact
    TrivialFix

    Change-Id: I32c0edbee4de14c8a0cc7c961d566e84d70f19a4

[Christian Berendt (berendt)]

Jeffrey, can you please add the missing docs.

[Jeffrey Zhang (jeffrey4l)]

This is an automated cleanup. This bug report has been closed because it
is older than 18 months and there is no open code change to fix this.
After this time it is unlikely that the circumstances which lead to
the observed issue can be reproduced.

If you can reproduce the bug, please:
* reopen the bug report (set to status "New")
* AND add the detailed steps to reproduce the issue (if applicable)
* AND leave a comment "CONFIRMED FOR: <RELEASE_NAME>"
  Only still supported release names are valid (OCATA, PIKE, QUEENS, ROCKY, ROCKY).
  Valid example: CONFIRMED FOR: OCATA