Added a procedure and edits to HA guide

Added a procedure for the MySQL with Galera page. Also made
punctuation changes (commas), and added an extra line of
content for the introduction paragraph. Changed procedure from
implicit to explicit numbering for impending xml conversion.

Change-Id: I9a82e8c945e03eb5a616031559ada026c3548c01
backport: none
Closes-Bug: #1319624
Merge "Added a procedure and edits to HA guide"