limit vehicle_command subscription updates per cycle

- this is a precaution to eliminate the possibility of getting stuck in
a loop trying to keep up with a high rate publication that could be
coming from a higher priority task

src/modules/mavlink/mavlink_main.cpp

@@ -2313,9 +2313,12 @@ Mavlink::task_main(int argc, char *argv[])
 		}
 
 
-		// vehicle_command
+		// MAVLINK_MODE_IRIDIUM: handle VEHICLE_CMD_CONTROL_HIGH_LATENCY
 		if (_mode == MAVLINK_MODE_IRIDIUM) {
-			while (_vehicle_command_sub.updated()) {
+			int vehicle_command_updates = 0;
+
+			while (_vehicle_command_sub.updated() && (vehicle_command_updates < vehicle_command_s::ORB_QUEUE_LENGTH)) {
+				vehicle_command_updates++;
 				const unsigned last_generation = _vehicle_command_sub.get_last_generation();
 				vehicle_command_s vehicle_cmd;
 

src/modules/mavlink/streams/COMMAND_LONG.hpp

@@ -62,8 +62,12 @@ private:
 		bool sent = false;
 
 		static constexpr size_t COMMAND_LONG_SIZE = MAVLINK_MSG_ID_COMMAND_LONG_LEN + MAVLINK_NUM_NON_PAYLOAD_BYTES;
+		int vehicle_command_updates = 0;
 
-		while ((_mavlink->get_free_tx_buf() >= COMMAND_LONG_SIZE) && _vehicle_command_sub.updated()) {
+		while ((_mavlink->get_free_tx_buf() >= COMMAND_LONG_SIZE)
+		       && _vehicle_command_sub.updated() && (vehicle_command_updates < vehicle_command_s::ORB_QUEUE_LENGTH)) {
+
+			vehicle_command_updates++;
 
 			const unsigned last_generation = _vehicle_command_sub.get_last_generation();
 			vehicle_command_s cmd;

src/modules/navigator/navigator_main.cpp

@@ -223,7 +223,10 @@ void Navigator::run()
 		_home_pos_sub.update(&_home_pos);
 
 		// Handle Vehicle commands
-		while (_vehicle_command_sub.updated()) {
+		int vehicle_command_updates = 0;
+
+		while (_vehicle_command_sub.updated() && (vehicle_command_updates < vehicle_command_s::ORB_QUEUE_LENGTH)) {
+			vehicle_command_updates++;
 			const unsigned last_generation = _vehicle_command_sub.get_last_generation();
 
 			vehicle_command_s cmd{};

src/modules/temperature_compensation/TemperatureCompensationModule.cpp

@@ -194,7 +194,10 @@ void TemperatureCompensationModule::Run()
 	perf_begin(_loop_perf);
 
 	// Check if user has requested to run the calibration routine
-	while (_vehicle_command_sub.updated()) {
+	int vehicle_command_updates = 0;
+
+	while (_vehicle_command_sub.updated() && (vehicle_command_updates < vehicle_command_s::ORB_QUEUE_LENGTH)) {
+		vehicle_command_updates++;
 		vehicle_command_s cmd;
 
 		if (_vehicle_command_sub.copy(&cmd)) {