tmpfiles: don't recursively descend into journal directories in /var

Do so only in /run. We shouldn't alter ACLs for existing files in /var,
but only for new files. If the admin made changes to the ACLs they
shouls stay in place.

We should still do recursive ACL changes for files in /run, since those
are not persistent, and will hence lack ACLs on every boot.

Also, /var/log/journal might be quit large, /run/log/journal is usually
not, hence we should avoid the recursive descending on /var, but not on
/run.

Fixes #534

(cherry picked from commit 8b258a64)