TMSS-60: bug fix: do keep track of previous state value

SAS/TMSS/src/tmss/tmssapp/models/scheduling.py

@@ -185,6 +185,8 @@ class Subtask(BasicCommon):
             except Exception as e:
                 logger.error("Could not send state change to messagebus: %s", e)
 
+            # update the previous state value
+            self.__original_state = self.state
 
 class SubtaskStateLog(BasicCommon):
     """