Only retain control-port connections

When MIDI input follows selection, ports that provide music-data
should be disconnected, even if they *also* provide control-data

libs/ardour/session_midi.cc

@@ -750,7 +750,7 @@ Session::rewire_selected_midi (boost::shared_ptr<MidiTrack> new_midi_target)
 			 * functionality.
 			 */
 
-			if (!(mpi.properties & MidiPortControl)) {
+			if (MidiPortControl != mpi.properties) {
 				/* disconnect the port from everything */
 				AudioEngine::instance()->disconnect (*p);
 			}