MDEV-12684 Show what config file a sysvar got a value from

change get_one_option() prototype to pass the filename and
not to pass the redundant optid.

client/mysql_plugin.c

@@ -474,11 +474,10 @@ static void print_default_values(void)
 */
 
 static my_bool
-get_one_option(int optid,
-               const struct my_option *opt __attribute__((unused)),
-               char *argument)
+get_one_option(const struct my_option *opt,
+               char *argument, const char *filename __attribute__((unused)))
 {
-  switch(optid) {
+  switch(opt->id) {
   case 'n':
     opt_no_defaults++;
     break;