Rover: create persist_streamrates() callback to indicate persistence

APMrover2/GCS_Mavlink.cpp

@@ -509,12 +509,6 @@ void GCS_MAVLINK_Rover::handleMessage(mavlink_message_t* msg)
 {
     switch (msg->msgid) {
 
-    case MAVLINK_MSG_ID_REQUEST_DATA_STREAM:
-        {
-            handle_request_data_stream(msg, true);
-            break;
-        }
-
     case MAVLINK_MSG_ID_COMMAND_INT: {
         // decode packet
         mavlink_command_int_t packet;

APMrover2/GCS_Mavlink.h

@@ -30,6 +30,8 @@ protected:
 
     virtual bool in_hil_mode() const override;
 
+    bool persist_streamrates() const override { return true; }
+
 private:
 
     void handleMessage(mavlink_message_t * msg) override;