QPID-5768 : Allow authenticated LDAP search

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1612381 13f79535-47bb-0310-9956-ffa450edef68
QPID-5768 : Fix error message

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1612382 13f79535-47bb-0310-9956-ffa450edef68