collectd ignores command line argument "-P"

Hi,
```man collectd``` says
```
Options
       [...]
       -P <pid-file>
           Specify an alternative pid file. This overwrites any settings in the config file. This is thought for
           init-scripts that require the PID-file in a certain directory to work correctly. For everyday-usage use
           the PIDFile config-option.
```

That doesn't work:

1. Make sure your collectd configuration file ```/etc/collectd.conf``` contains ```PIDFile``` setting, e.g. ```PIPFile /run/collectd/collectd-from-conf.pid```

2. Now start collectd like ```/usr/sbin/collectd -C /etc/collectd.conf -P /tmp/collectd-from-cli.pid```

You will see that ```/tmp/collectd-from-cli.pid``` won't be created but ```/run/collectd/collectd-from-conf.pid```.


Tested with collectd-5.4.0.