tests/multi_net: Fix TCP accept test when using system error numbers.

If a port is not using internal error numbers, which match both lwIP and
Linux error numbers, ENTOCONN from standard libraries errno.h equals 128,
not 107.

tests/multi_net/tcp_accept_recv.py

@@ -17,7 +17,7 @@ def instance0():
     try:
         print("recv", s.recv(10))  # should raise Errno 107 ENOTCONN
     except OSError as er:
-        print(er.errno)
+        print(er.errno in (107, 128))
     s.close()