Ignore rights in libpreopen. (#129)

Ignore rights in libpreopen. (#129)

Don't ignore paths which don't have the required rights. This means
that if the lookup finds a path that doesn't have the required
rights, it'll just proceed to the actual operation which will fail
with `ENOTCAPABLE`.

Intuitively, use cases which would depend on having multiple
overlapping matching paths for a given lookup and intelligently
picking the one with the required rights seems like they should
be uncommon.

This is simpler overall, and requires less code.