mysql bootstrap fails in Debian Jessie

 /etc/init.d/mysql start --wsrep-new-cluster fails in Debian Jessie because the /lib/lsb/init-functions.d/40-systemd script redirects it to systemctl mysql start, losing the --wsrep-new-cluster argument in the process. The solution is to set the _SYSTEMCTL_SKIP_REDIRECT variable so that all handling of "mysql start" remains within the script we provide.

A similar solution was used for OpenSuse.
