Install and configure for Red Hat Enterprise Linux and CentOS in freezer

[Father Vlasie]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [x] This doc is inaccurate in this way:

These commands do not work when executed in the place the doc indicates:

    sudo cp etc/freezer/freezer-api.conf.sample /etc/freezer/freezer-api.conf
    sudo cp etc/freezer/freezer-paste.ini /etc/freezer/freezer-paste.ini

cp: cannot stat ‘etc/freezer/freezer-api.conf.sample’: No such file or directory

I tried adding a slash to the beginning but to no avail. Do we need to install freezer first? Are we missing a step in the doc?

- [ ] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

-----------------------------------
Release: 7.0.0.0b2.dev8 on 2018-04-26 13:23
SHA: 1ebd6d12efb78bbaac0ba454ab03d52659dddfde
Source: https://git.openstack.org/cgit/openstack/freezer/tree/doc/source/install/install-rdo.rst
URL: https://docs.openstack.org/freezer/latest/install/install-rdo.html