Low: CTS: Fix regexes for new /etc/sysconfig/pacemaker syntax.

0c3631e96973481cda230de410dda8a05fd8877e changed that file such that the
existing regexes weren't really useful anymore. In particular, the file
previously only had each key listed once while it now has each listed
several times. Thus, the regexes that just looked for the key and
changed it would now perform the substitution in several spots,
potentially breaking settings.

Instead, try to be smarter and only apply the substitutions in the one
place where they're needed while also using simpler regexes and
commenting what exactly they do.

Note that there's one behavioral change here:

trace-add can now only be run if trace-set has been run first to ensure
an uncommented PCMK_trace_functions line exists. There's not really any
readable one line sed command that can both create the line if it
doesn't exist, and add to it if it does. Hopefully this isn't too big
of a change.