MDEV-14205 Windows : fix race condition writing into error log and setvbuf

Do not do reopen_fstreams/setbuf twice during server startup on Windows.
fprintf(stderr,..) might crash, if setbuf is executed at the same time.

sql/mysqld.cc

@@ -5747,9 +5747,6 @@ int mysqld_main(int argc, char **argv)
 #ifdef __WIN__
   if (!opt_console)
   {
-    if (reopen_fstreams(log_error_file, stdout, stderr))
-      unireg_abort(1);
-    setbuf(stderr, NULL);
     FreeConsole();				// Remove window
   }