QPID-3396 Modified the URLParser to not throw an exception if the
username and password is empty. Instead once a SASL mechanism is
selected we check if that mechanism needs user/pass and then throw an
exception at that point.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1453558 13f79535-47bb-0310-9956-ffa450edef68
QPID-3396 Changed the test cases to relect that username and password
is optional.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1453559 13f79535-47bb-0310-9956-ffa450edef68