workflows: add ip prefix duplicate check / fix duplicates

[Noki]

This ensures that we do not have duplicate IP prefixes any more:

closes #901

[FFHener]

Thank you for writing this check. It feels kind of hacky to use a bash-script with a regex. Could there be a cleaner way using ansible tasks instead as it interprets everything as variables and not just as a random text file?

[Noki]

Thank you for writing this check. It feels kind of hacky to use a bash-script with a regex. Could there be a cleaner way using ansible tasks instead as it interprets everything as variables and not just as a random text file?

Using ansible would be cleaner, but that's nothing I can do right now. Feel free to add an issue to rewrite this later on when someone has time. For now any check is better than no check.

This is ready for review and to be merged.

[FFHener]

Lgtm, but I am not an shell expert. We might want an additional review

[pktpls]

This is the kind of linter I like :) can be run locally and solves a real problem 👍

Also add them to make lint when all are merged. - oh wait, make lint doesn't exist here yet