Vehicle: independent function to delete gimbal controller, needed for tests:

RequestMessageTest implementation collides with how gimbal controller works.
Gimbal controller will request some messages when hearbeat is received, to
try to discover new gimbals, and it messes with this particular test, so this
way we can disable gimbal manager just for this test

src/Vehicle/Vehicle.cc

@@ -519,8 +519,7 @@ Vehicle::~Vehicle()
     delete _mav;
     _mav = nullptr;
 
-    delete _gimbalController;
-    _gimbalController = nullptr;
+    deleteGimbalController();
 }
 
 void Vehicle::prepareDelete()
@@ -536,6 +535,14 @@ void Vehicle::prepareDelete()
     }
 }
 
+void Vehicle::deleteGimbalController()
+{
+    if (_gimbalController) {
+        delete _gimbalController;
+        _gimbalController = nullptr;
+    }
+}
+
 void Vehicle::_offlineFirmwareTypeSettingChanged(QVariant varFirmwareType)
 {
     _firmwareType = static_cast<MAV_AUTOPILOT>(varFirmwareType.toInt());

src/Vehicle/Vehicle.h

@@ -898,6 +898,9 @@ public:
     /// Vehicle is about to be deleted
     void prepareDelete();
 
+    /// Delete gimbal controller, handy for RequestMessageTest.cc, otherwise gimbal controller message requests will mess with this test
+    void deleteGimbalController();
+
     quint64     mavlinkSentCount        () const{ return _mavlinkSentCount; }        /// Calculated total number of messages sent to us
     quint64     mavlinkReceivedCount    () const{ return _mavlinkReceivedCount; }    /// Total number of sucessful messages received
     quint64     mavlinkLossCount        () const{ return _mavlinkLossCount; }        /// Total number of lost messages