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