Rudder

This is essentially the same as #5825 but on the 2.11 branch, and with improvements.

'killall' may not be available, and sometimes it is known to fail:

[root@server ~]# ps axf | grep [s]lapd
4387 ?        Ssl    0:05 /opt/rudder/libexec/slapd -h ldap://127.0.0.1:389 -n rudder-slapd -f /opt/rudder/etc/openldap/slapd.conf
[root@server ~]# /usr/bin/killall -KILL /opt/rudder/libexec/slapd
/opt/rudder/libexec/slapd: no process killed

However, we can use "pidof". But the original implementation in #5825 only looked for pidof in /bin, although it can be elsewhere (like /sbin, on RHEL 6 at least).