This commit fixes two bugs:
1) When starting a github-runner for the very first time, the
unconfigure script did not copy the `tokenFile` to the state
directory. This case just was not handled so far. As a result, the
runner could not configure. The unit did, however, fail even before
as the state token file is configured as inaccessible for the service
through `InaccessiblePaths=`. As the given path did not exist in the
described case, setting up the unit's namespacing failed.
2) Similarly, the `tokenFile` is also marked as not accessible to the
service user. There are, however, cases where other namespacing
options make the files inaccessible even before `InaccessiblePaths=`
kicks in; thus, they appear as non existing and cause the namespacing
to fail yet again. Prefixing the entry with a `-` causes Systemd to
ignore the entry if it cannot find it. This is the behavior we want.
I also took fixing those bugs as a chance to refactor the unconfigure
script to make it easier to follow.
941c79b620