Rename snuffleupagus  rule param from var_name to varname

See merge request !1

we still need to reload systemd otherwise puppet might try to activate the socket before the .service is loaded and we get Socket service fpm-xyz.service not loaded

Systemd tells us:

Configuration file /etc/systemd/system/fpm-xyz.socket is marked
world-inaccessible. This has no effect as configuration data is
accessible via APIs without restrictions. Proceeding anyway.

PHPMailer sets the envelope from via additional_params. Lets whitelist
a parameter that consists solely of `-femail@domain.com`.

This is using a slightly restricted subset of characters that are valid
 in emails. But doing something more precise there seems like overkill.

eat some more backspace