OAK-1942 : UserAuthentication: enhance login states with relevant exceptions (patch provided by Dominique Jaeggi, thanks a lot!)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1607805 13f79535-47bb-0310-9956-ffa450edef68
OAK-1943

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1607820 13f79535-47bb-0310-9956-ffa450edef68