The "reload_config" command doesn't work the way admins would typically
expect, so it shouldn't be exposed via systemd. Those who understand
the behavior can execute the command using ejabberdctl.
Admins might expect ejabberd to be able to access data below /home or
/tmp. For example, they might use those locations to dump/restore
Mnesia backups, or as a document root for mod_http_fileserver or
mod_http_upload.
Fixes#1297.
