Log file metric exporter is still following /var/log/containers files.

The log file metric exporter is still following files via their /var/log/containers path.

This is now a symlink to /var/log/pods.

This works fine, but we should update the exporter to read /var/log/containers directly, since /var/log/containers is deprecated and will eventually go away.

The exporter is already able to follow symlinks or regular files, so this requires:

• having it read from the /var/log/pods directory
• updating its labels regular expression for the format of paths under this directory