Make Connection.isClosed return True on aborted connections.

The only difference between an aborted connection and a closed one is that
packets sent just before aborting are pushed to the network before really
closing the connection. But further sends must fail, and nothing should be
received.

neo/lib/connection.py

@@ -329,7 +329,7 @@ class BaseConnection(object):
         return None
 
     def isClosed(self):
-        return self.connector is None
+        return self.connector is None or self.isAborted()
 
     def isAborted(self):
         return False

neo/lib/handler.py

@@ -122,7 +122,6 @@ class EventHandler(object):
     # Packet handlers.
 
     def ping(self, conn):
-        if not conn.isAborted():
         conn.answer(Packets.Pong())
 
     def pong(self, conn):

neo/storage/app.py

@@ -354,7 +354,7 @@ class Application(object):
                 event_queue_dict[key] -= 1
                 if event_queue_dict[key] == 0:
                     del event_queue_dict[key]
-            if conn.isAborted() or conn.isClosed():
+            if conn.isClosed():
                 continue
             orig_msg_id = conn.getPeerId()
             conn.setPeerId(msg_id)