[tests] Don't call super twice in P2PTxInvStore.on_inv()

Author: jnewbery

test/functional/test_framework/mininode.py

@@ -658,8 +658,6 @@ def on_inv(self, message):
                 # save txid
                 self.tx_invs_received[i.hash] += 1
 
-        super().on_inv(message)
-
     def get_invs(self):
         with mininode_lock:
             return list(self.tx_invs_received.keys())