tests/connect_nonblock: Refactor towards real net_hosted test.

In the future, a special runner for such tests will import each test and
call test() function with an address of test server to use.

tests/net_hosted/connect_nonblock.py

@@ -5,10 +5,16 @@ try:
 except:
     import socket
 
+
+def test(peer_addr):
     s = socket.socket()
     s.setblocking(False)
     try:
-    s.connect(socket.getaddrinfo('micropython.org', 80)[0][-1])
+        s.connect(peer_addr)
     except OSError as er:
         print(er.args[0] == 115) # 115 is EINPROGRESS
     s.close()
+
+
+if __name__ == "__main__":
+    test(socket.getaddrinfo('micropython.org', 80)[0][-1])