Remove duplicate method definitions in NodeConnCB subclasses

All Node classes in individual test cases subclass from NodeConnCB. Many
have duplicate definitions for methods that are defined in the base
class. This commit removes those duplicate definitions.

This commit removes ~290 lines of duplicate code.

test/functional/p2p-leaktests.py

@@ -20,17 +20,9 @@ banscore = 10
 class CLazyNode(NodeConnCB):
     def __init__(self):
         super().__init__()
-        self.connection = None
         self.unexpected_msg = False
-        self.connected = False
         self.ever_connected = False
 
-    def add_connection(self, conn):
-        self.connection = conn
-
-    def send_message(self, message):
-        self.connection.send_message(message)
-
     def bad_message(self, message):
         self.unexpected_msg = True
         self.log.info("should not have received message: %s" % message.command)
@@ -65,9 +57,6 @@ class CLazyNode(NodeConnCB):
 # Node that never sends a version. We'll use this to send a bunch of messages
 # anyway, and eventually get disconnected.
 class CNodeNoVersionBan(CLazyNode):
-    def __init__(self):
-        super().__init__()
-
     # send a bunch of veracks without sending a message. This should get us disconnected.
     # NOTE: implementation-specific check here. Remove if bitcoind ban behavior changes
     def on_open(self, conn):