[tests] Make NodeConnCB a subclass of NodeConn

This makes NodeConnCB a subclass of NodeConn, and
removes the need for the client code to know
anything about the implementation details of NodeConnCB.

NodeConn can now be swapped out for any other implementation
of a low-level connection without changing client code.

test/functional/test_framework/test_node.py

@@ -14,7 +14,6 @@ import subprocess
 import time
 
 from .authproxy import JSONRPCException
-from .mininode import NodeConn
 from .util import (
     assert_equal,
     get_rpc_proxy,
@@ -158,7 +157,7 @@ class TestNode():
         self.encryptwallet(passphrase)
         self.wait_until_stopped()
 
-    def add_p2p_connection(self, p2p_conn, **kwargs):
+    def add_p2p_connection(self, p2p_conn, *args, **kwargs):
         """Add a p2p connection to the node.
 
         This method adds the p2p connection to the self.p2ps list and also
@@ -167,9 +166,9 @@ class TestNode():
             kwargs['dstport'] = p2p_port(self.index)
         if 'dstaddr' not in kwargs:
             kwargs['dstaddr'] = '127.0.0.1'
+
+        p2p_conn.peer_connect(*args, **kwargs)
         self.p2ps.append(p2p_conn)
-        kwargs.update({'callback': p2p_conn})
-        p2p_conn.add_connection(NodeConn(**kwargs))
 
         return p2p_conn
 
@@ -185,10 +184,8 @@ class TestNode():
     def disconnect_p2ps(self):
         """Close all p2p connections to the node."""
         for p in self.p2ps:
-            # Connection could have already been closed by other end.
-            if p.connection is not None:
-                p.connection.disconnect_node()
-        self.p2ps = []
+            p.peer_disconnect()
+        del self.p2ps[:]
 
 
 class TestNodeCLI():