efl_ui_relative_layout: prevent infinite loop in chain calculation

efl_ui_relative_layout: prevent infinite loop in chain calculation

Test Plan:
test code
```
EAPI_MAIN int
elm_main(int argc, char **argv)
{
   Eo *win, *layout, *btn1, *btn2, *btn3;

   win =  efl_add(EFL_UI_WIN_CLASS, efl_main_loop_get());
   layout = efl_add(EFL_UI_RELATIVE_LAYOUT_CLASS, win,
                    efl_content_set(win, efl_added));

   btn1 = efl_add(EFL_UI_BUTTON_CLASS, layout);
   btn2 = efl_add(EFL_UI_BUTTON_CLASS, layout);

   efl_ui_relative_layout_relation_right_set(layout, btn1, btn2, 0.0);
   efl_ui_relative_layout_relation_right_set(layout, btn2, btn1, 0.0);

   efl_ui_relative_layout_relation_left_set(layout, btn2, btn1, 1.0);
   efl_ui_relative_layout_relation_left_set(layout, btn1, btn2, 1.0);

   elm_run();
   return 0;
}
ELM_MAIN()
```

Reviewers: Jaehyun_Cho

Reviewed By: Jaehyun_Cho

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D9032