Use LOCK_show_status when we add things to all_status_vars

This was missing in my last commit for fixing possible lockups in SHOW STATUS.

sql/log.cc:
  Fixed comment
sql/sql_show.cc:
  Use LOCK_show_status when we add things to all_status_vars
sql/sql_test.cc:
  Remove not needed mutex_lock

sql/log.cc

@@ -9640,7 +9640,7 @@ set_binlog_snapshot_file(const char *src)
   Copy out current values of status variables, for SHOW STATUS or
   information_schema.global_status.
 
-  This is called only under LOCK_status, so we can fill in a static array.
+  This is called only under LOCK_show_status, so we can fill in a static array.
 */
 void
 TC_LOG_BINLOG::set_status_variables(THD *thd)

sql/sql_show.cc

@@ -2846,7 +2846,7 @@ int add_status_vars(SHOW_VAR *list)
 {
   int res= 0;
   if (status_vars_inited)
-    mysql_mutex_lock(&LOCK_status);
+    mysql_mutex_lock(&LOCK_show_status);
   if (!all_status_vars.buffer && // array is not allocated yet - do it now
       my_init_dynamic_array(&all_status_vars, sizeof(SHOW_VAR), 200, 20, MYF(0)))
   {
@@ -2861,7 +2861,7 @@ int add_status_vars(SHOW_VAR *list)
     sort_dynamic(&all_status_vars, show_var_cmp);
 err:
   if (status_vars_inited)
-    mysql_mutex_unlock(&LOCK_status);
+    mysql_mutex_unlock(&LOCK_show_status);
   return res;
 }
 
@@ -2923,7 +2923,7 @@ void remove_status_vars(SHOW_VAR *list)
 {
   if (status_vars_inited)
   {
-    mysql_mutex_lock(&LOCK_status);
+    mysql_mutex_lock(&LOCK_show_status);
     SHOW_VAR *all= dynamic_element(&all_status_vars, 0, SHOW_VAR *);
 
     for (; list->name; list++)
@@ -2944,7 +2944,7 @@ void remove_status_vars(SHOW_VAR *list)
       }
     }
     shrink_var_array(&all_status_vars);
-    mysql_mutex_unlock(&LOCK_status);
+    mysql_mutex_unlock(&LOCK_show_status);
   }
   else
   {

sql/sql_test.cc

@@ -575,7 +575,6 @@ void mysql_print_status()
   /* Print key cache status */
   puts("\nKey caches:");
   process_key_caches(print_key_cache_status, 0);
-  mysql_mutex_lock(&LOCK_status);
   printf("\nhandler status:\n\
 read_key:   %10lu\n\
 read_next:  %10lu\n\
@@ -591,7 +590,6 @@ update:     %10lu\n",
 	 tmp.ha_write_count,
 	 tmp.ha_delete_count,
 	 tmp.ha_update_count);
-  mysql_mutex_unlock(&LOCK_status);
   printf("\nTable status:\n\
 Opened tables: %10lu\n\
 Open tables:   %10lu\n\