(doc) Reorder changes to ejabberd.cfg in install instructions

I found it annoying that the list of changes to make to ejabberd.cfg
didn't follow the order that the options showed up in the default
Debian ejabberd.cfg.  I reordered them so after you finish changing one
option, you can search forward in the document for the next term.

(From Github pull request #3.)

Signed-off-by: Josh Stompro <Stomproj@larl.org>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>