QPID-4746, QPID-4747: remove the defaultAuthenticationProvider attribute from broker and add an overriding authentication provider for management mode

merged from trunk r1468830


git-svn-id: https://svn.apache.org/repos/asf/qpid/branches/0.22@1469915 13f79535-47bb-0310-9956-ffa450edef68