Improve install guide ceilometer controller

I improved the ceilometer controller section in the installation
guide as follows:

1) Renamed file and XML IDs to agree with similar content.
2) Reordered instructions.

Implements: blueprint installation-guide-improvements
Co-Authored-By: Matt Kassawara <mkassawara@gmail.com>

Change-Id: I13644b0d4f244be3018d13f3fb5544287277770c