Tmpfiles.d processing had /run overriding /usr/lib and /etc, but this is
not correct. The correct order, from lowest to highest, for tmpfiles
processing is:
* /usr/lib/tmpfiles.d/*.conf
* /run/tmpfiles.d/*.conf
* /etc/tmpfiles.d
This means /run/tmpfiles.d/*.conf can override /etc/tmpfiles.d/*.conf,
but /etc/tmpfiles.d/*.conf can override both of them.
This fixes#49.