stop and restart fail in Debian 10 buster

Debian 10 "buster" has an updated start-stop-daemon version that causes init script to fail to stop or restart Cassandra daemon. stop option do not stops first launched instance and depending of previous operations, restart and start could launch a second Cassandra daemon instance.

start-stop-daemon since version 1.19.3 fail to stop matching only a pidfile that can be writen by an unprivileged (non-root) user because it is considered a security risk.

Adding a second matching option (user) solved this.

This fix does not break compatibility with older versions and does not mess with pidfile's mode or permissions.

Related: CASSANDRA-15099

https://github.com/vice/cassandra/tree/debian-buster