Ensure socket closes properly

The socket is being held open by the writable handle. Close both the handle and the socket.
To do this we need to store the handle as a member variable.

rpdb/__init__.py

@@ -59,13 +59,16 @@ def __init__(self, addr=DEFAULT_ADDR, port=DEFAULT_PORT):
                          stdin=FileObjectWrapper(handle, self.old_stdin),
                          stdout=FileObjectWrapper(handle, self.old_stdin))
         sys.stdout = sys.stdin = handle
+        self.handle = handle
         OCCUPIED.claim(port, sys.stdout)
 
     def shutdown(self):
         """Revert stdin and stdout, close the socket."""
         sys.stdout = self.old_stdout
         sys.stdin = self.old_stdin
+        self.handle.close()
         OCCUPIED.unclaim(self.port)
+        self.skt.shutdown(socket.SHUT_RDWR)
         self.skt.close()
 
     def do_continue(self, arg):