Modified LDAP authentication to support a lookup for the NRS system. If
the auth on the provided string fails as a DN, try to look up a new
DN based on the UID. If we get a match, use that DN for auth and see
if that works. This allows us to use a referral within the
dc=ecoinformatics,dc=org tree to point at distinguished names that are
rooted in another tree (such as ou=People,o=ucnrs.org).