Bug#962412: OpenRC and LSB header logic

[Jesse Smith]

I have imported the patch to check for OpenRC headers upstream. This
change will appear in version 1.22.0 of insserv.

I accepted in the modification from Tito to make the check for OpenRC
scripts more robust.

Please let me know if there are any additional changes to be made to
make sure insserv properly handled finding an OpenRC script.

- Jesse