fix(gvm): Properly destroys all variables in the gvm

- When exiting the GUI or ending the core/start.py script, now a function will be called to properly delete all variables in the global variable manager
- Improves dealing with threads and spinning nodes (ROS2)

source/rafcon/core/global_variable_manager.py

@@ -310,6 +310,17 @@ def get_all_keys_starting_with(self, start_key):
             if g_key and start_key in g_key:
                 output_list.append(g_key)
         return output_list
+
+    def destroy_all_variables(self):
+        """ Deletes all global variables in a loop and then clears access keys and 
+        type dictionary. Is called on shutdown.
+
+        """
+        for key in list(self.__global_variable_dictionary):
+            self.delete_variable(key)
+        self.reset()
+
+        logger.debug("All global variables were deleted!")
 
 #########################################################################
 # Properties for all class fields that must be observed by gtkmvc3

source/rafcon/core/start.py

@@ -333,7 +333,13 @@ def main(optional_args=None):
             time.sleep(1)
 
     logger.info("State machine execution finished!")
+
     plugins.run_hook("post_destruction")
+
+    # Properly destroy all global variables
+    gvm = core_singletons.global_variable_manager
+    gvm.destroy_all_variables()
+
     logging.shutdown()
 
     if user_input.memory_profiling:

source/rafcon/gui/start.py

@@ -299,6 +299,10 @@ def stop_gtk():
 def post_gui_destruction():
     plugins.run_hook("post_destruction")
 
+    # Properly destroy all global variables
+    gvm = core_singletons.global_variable_manager
+    gvm.destroy_all_variables()
+
     if global_gui_config.get_config_value('AUTO_RECOVERY_LOCK_ENABLED'):
         import rafcon.gui.models.auto_backup
         rafcon.gui.models.auto_backup.remove_rafcon_instance_lock_file()