mavlink: match commands aimed at any sysid/compid

When we send a command to any sysid or any compid, we need to match an
ack from a specific sysid or compid. If we don't do that, we keep
sending retransmissions and eventually time out.

src/modules/mavlink/mavlink_command_sender.cpp

@@ -123,8 +123,8 @@ void MavlinkCommandSender::handle_mavlink_command_ack(const mavlink_command_ack_
 	while (command_item_t *item = _commands.get_next()) {
 		// Check if the incoming ack matches any of the commands that we have sent.
 		if (item->command.command == ack.command &&
-		    from_sysid == item->command.target_system &&
-		    from_compid == item->command.target_component &&
+		    (item->command.target_system == 0 || from_sysid == item->command.target_system) &&
+		    (item->command.target_component == 0 || from_compid == item->command.target_component) &&
 		    item->num_sent_per_channel[channel] != -1) {
 			item->num_sent_per_channel[channel] = -2;	// mark this as acknowledged
 			break;