add qpid username and password parameters

https://bugzilla.redhat.com/show_bug.cgi?id=1038766
These changes pretty closely follow https://review.openstack.org/#/c/58898/

This has been smoke tested with nova-network controller+compute, neutron controller+compute+networker.  It has only been tested with a non-empty $qpid_username/$qpid_password.  An empty $qpid_username and $qpid_password should be equivalent to the old 'auth => "no"' case.