Alpine Linux 3.21 docker image no longer has lockfile dir

[rdmark]

As of v3.21, Alpine Linux no longer has a default lockfile dir. Previously /var/lock which was then turned into a symlink to /run/lock. But now /run/lock doesn't exist by default either.

So the assumptions about the lockdir in our code is no longer valid, leading to netatalk erroring out when it cannot create its lockfile.

[rdmark]

This seems to be a problem only on the base OS docker image for Alpine 3.21. When installing the full OS you get the /run/lock dir by default.

[rdmark]

Being fixed upstream in Alpine (commit from 15h ago at the time of writing)

https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/69233

[rdmark]

Tracked for the Alpine docker image in alpinelinux/docker-alpine#433