multi: inform about closed sockets before they are closed

When the connection code decides to close a socket it informs the multi
system via the Curl_multi_closed function. The multi system may, in
turn, invoke the CURLMOPT_SOCKETFUNCTION function with
CURL_POLL_REMOVE. This happens after the socket has already been
closed. Reorder the code so that CURL_POLL_REMOVE is called before the
socket is closed.

lib/connect.c

@@ -1244,12 +1244,13 @@ int Curl_closesocket(struct connectdata *conn,
     else
       return conn->fclosesocket(conn->closesocket_client, sock);
   }
-  sclose(sock);
 
   if(conn)
     /* tell the multi-socket code about this */
     Curl_multi_closed(conn, sock);
 
+  sclose(sock);
+
   return 0;
 }