Fix in docker_inspect_self_mountinfo() fo Gitlab runner

[zweikaesehoch]

Crossbuilding in our buildimage on a Gitlab runner failed:

Container ID could not be resolved from /proc/self/mountinfo, because "/docker/" string was expected, but "/docker-data/" provided:

I extended string matching with "/docker-data/" and our pipeline is working again.

[Emilgardis]

Thanks!

[zweikaesehoch]

We further investigated the error which led us to our custom data-root setting in /etc/docker/daemon.json:

The fallback implemented due to #1321 misses the container id because of our changed data-root to "docker-data" instead of default "docker".

The real issue here is, that docker_inspect_self_mountinfo() wont work, if data-root setting contains no "/docker/".

The current PR bears no value for other users now.
One would need to parse daemon.json data-root setting to make the fallback more robust.

Pseudocode:

Look into /etc/docker/daemon.json
if data-root is set
  extract last path element as DATA_ROOT
  if DATA_ROOT not equals "/docker"
    add DATA_ROOT to OR-filter strings in line 1367