Fixes #6842: Edit only one syslog configuration at a time

[Kegeruneku]

https://www.rudder-project.org/redmine/issues/6842

[peckpeck]

What if someone has an old configuration file that is not used because they have migrated from a daemon to another one ?

[Kegeruneku]

That's precisely the case I'm trying to solve: we want only one active configuration. rsyslog is becoming the de-facto standard, that's why I give it the top priority. Do you think I should use another indicator instead ?

[peckpeck]

I think there is no problem at all. Testing the existence of a file is almost free whereas you don't know the reason a user may have to change his syslog daemon. He can go from rsyslog to syslog-ng if he needs a new feature.
So I don't see any gain in doing this.