Create a new QDBusConnectionPrivate for every new connection in
qDBusNewConnection instead of creating a single QDBusConnectionPrivate
in the QDBusServer constructor which gets assigned the latest connected
DBusConnection in qDBusNewConnection (and loses track on all previous
DBusConnections).
Also extend tst_QDBusConnection::registerObjectPeer() test with multiple
connections to the server.
Task-Number: 24921
Change-Id: I4341e8d48d464f3fe0a314a6ab14f848545d65a0
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>