Add proper multikey support for EventHandlers with compatibility

lib/tfw/components/process_managing_event_handler.py

@@ -38,7 +38,6 @@ class ProcessManagingEventHandler(EventHandlerBase):
     """
     def __init__(self, key, dirmonitor=None, log_tail=0):
         super().__init__(key)
-        self.key = key
         self.monitor = dirmonitor
         self.processmanager = ProcessManager()
         self.log_tail = log_tail

lib/tfw/event_handler_base.py

@@ -20,10 +20,17 @@ class EventHandlerBase(ABC):
     """
     def __init__(self, key):
         self.server_connector = ServerConnector()
-        self.key = key
-        self.subscribe(self.key)
+        self.keys = [key]
+        self.subscribe(*self.keys)
         self.server_connector.register_callback(self.event_handler_callback)
 
+    @property
+    def key(self):
+        """
+        Returns the oldest key this EventHandler was subscribed to.
+        """
+        return self.keys[0]
+
     def event_handler_callback(self, message):
         """
         Callback that is invoked when receiving a message.
@@ -48,7 +55,7 @@ class EventHandlerBase(ABC):
         subscribed to 'fsm' will receive 'fsm_update'
         messages as well.
         """
-        return self.key == message['key']
+        return message['key'] in self.keys
 
     def dispatch_handling(self, message):
         """
@@ -80,6 +87,7 @@ class EventHandlerBase(ABC):
         """
         for key in keys:
             self.server_connector.subscribe(key)
+            self.keys.append(key)
 
     def unsubscribe(self, *keys):
         """
@@ -89,6 +97,7 @@ class EventHandlerBase(ABC):
         """
         for key in keys:
             self.server_connector.unsubscribe(key)
+            self.keys.remove(key)
 
     def cleanup(self):
         """