Fix the content and format of MaxScale-HA-with-Corosync-Pacemaker document

Several issues with https://github.com/mariadb-corporation/MaxScale/blob/master/Documentation/Reference/MaxScale-HA-with-Corosync-Pacemaker.md

(1) The title should not say "Content" but "MaxScale HA with Corosync Pacemaker"
(2) Through out the document sections are not properly titled. Statements that should not be section or subsection title are in Bold huge fonts.
(3) Document is not easy to follow.

Once you have fixed above in separate branch please share the link with Dipti to review, before checking in the changes.