Bind propagation no longer valid for volume mounting

Summary

We cannot use bind-propagation when specifying volumes.

On #4276 (closed) Z modes where not working. It got fixed but it only took SELinux labels into account, not bind-propagation which was working before.

This forces CERN to keep on using an old version (11.10), not matching our GitLab instance. This will make us miss any extra features that require a version update.

Steps to reproduce

Configure a runner to use /examplemounts/example/:/example:rslave as a volume.

Actual behavior

When picking a job:

WARNING: Job failed: invalid volume specification: "/examplemounts/example/:/example:rslave"

Expected behavior

The volume should be valid, just as on v11.10.0.

Used GitLab Runner version

Works on 11.10.X.

It does not on 12.0.2

Possible fixes

On https://gitlab.com/gitlab-org/gitlab-runner/blob/fc259ef2854bef46e5357bf28f5b8239e185ea6e/executors/docker/internal/volumes/parser/linux_parser.go#L14 it should allow bind propagation as well, not only SELinux labels.