Files in pkg/util/mount that contain significant code implementation for
subpaths are moved to a new package at pkg/volume/util/subpath. This
move is done in order to preserve git history.
Users must not be allowed to step outside the volume with subPath.
Therefore the final subPath directory must be "locked" somehow
and checked if it's inside volume.
On Windows, we lock the directories. On Linux, we bind-mount the final
subPath into /var/lib/kubelet/pods/<uid>/volume-subpaths/<container name>/<subPathName>,
it can't be changed to symlink user once it's bind-mounted.
NsEnterMounter should not stop parsing findmnt output on the first space but
on the last one, just in case the mount point name itself contains a space.
