Fix wsrep.variables test case

Correctly port 09b25f85 from 10.0.

Expose check_is_super via include file to allow wsrep_on_check to use
it.

sql/set_var.h

@@ -426,6 +426,7 @@ CHARSET_INFO *get_old_charset_by_name(const char *old_name);
 int sys_var_init();
 int sys_var_add_options(DYNAMIC_ARRAY *long_options, int parse_flags);
 void sys_var_end(void);
+bool check_has_super(sys_var *self, THD *thd, set_var *var);
 
 #endif
 

sql/sys_vars.cc

@@ -428,7 +428,7 @@ error_if_in_trans_or_substatement(THD *thd, int in_substatement_error,
   return false;
 }
 
-static bool check_has_super(sys_var *self, THD *thd, set_var *var)
+bool check_has_super(sys_var *self, THD *thd, set_var *var)
 {
   DBUG_ASSERT(self->scope() != sys_var::GLOBAL);// don't abuse check_has_super()
 #ifndef NO_EMBEDDED_ACCESS_CHECKS

sql/wsrep_var.cc

@@ -69,6 +69,9 @@ bool wsrep_on_check(sys_var *self, THD* thd, set_var* var)
 {
   bool new_wsrep_on= (bool)var->save_result.ulonglong_value;
 
+  if (check_has_super(self, thd, var))
+    return true;
+
   if (new_wsrep_on && innodb_lock_schedule_algorithm != 0) {
     my_message(ER_WRONG_ARGUMENTS, " WSREP (galera) can't be enabled "
 	    "if innodb_lock_schedule_algorithm=VATS. Please configure"