MXS-1449 Sort case statements

Faster to later check for something specific.

server/modules/filter/dbfwfilter/dbfwfilter.c

@@ -2308,13 +2308,13 @@ static bool command_is_mandatory(const GWBUF *buffer)
 {
     switch (MYSQL_GET_COMMAND((uint8_t*)GWBUF_DATA(buffer)))
     {
-    case MYSQL_COM_QUIT:
-    case MYSQL_COM_PING:
     case MYSQL_COM_CHANGE_USER:
-    case MYSQL_COM_SET_OPTION:
     case MYSQL_COM_FIELD_LIST:
-    case MYSQL_COM_PROCESS_KILL:
+    case MYSQL_COM_PING:
     case MYSQL_COM_PROCESS_INFO:
+    case MYSQL_COM_PROCESS_KILL:
+    case MYSQL_COM_QUIT:
+    case MYSQL_COM_SET_OPTION:
         return true;
 
     default: