Fixed BUG#7620: Stored procedure packet error if show mutex status

  Another multi result statement added.
  Note: No test case, as it's not possible to get a deterministic result from this.


sql/sp_head.cc:
  Another multi result statement added: show mutex status.

sql/sp_head.cc

@@ -77,6 +77,7 @@ sp_multi_results_command(enum enum_sql_command cmd)
   case SQLCOM_SHOW_KEYS:
   case SQLCOM_SHOW_LOGS:
   case SQLCOM_SHOW_MASTER_STAT:
+  case SQLCOM_SHOW_MUTEX_STATUS:
   case SQLCOM_SHOW_NEW_MASTER:
   case SQLCOM_SHOW_OPEN_TABLES:
   case SQLCOM_SHOW_PRIVILEGES: