improve safety of -o option

[davidelang]

Expected behavior

rsyslog should not overwrite it's own config file

Actual behavior

I'm not sure exactly how, but I had an instance where a scripted restart ended up overwriting /etc/rsyslog.conf

Steps to reproduce the behavior

not sure
in /etc/init.d/rsyslog -o /etc/rsyslog.conf.generated was added to the startup line on centos.
something happened with an indirect restart (system restart or *ctl restart type of thing) and /etc/rsyslog.conf was overwritten and looks like it was generated by -o and is empty

make sure that we aren't overwriting the config file we are reading

Environment

• rsyslog version:
• platform:
• for configuration questions/issues, include rsyslog.conf and included config files