e_focus: add code to call e_client_focus_defer_set in mouse down callback

e_focus: add code to call e_client_focus_defer_set in mouse down callback

There is bug that the child window can not get focus when the mouse down event is occured.
In mouse down callback, the window get focus first.

If the window is child and it set the belong_to_parent property to the parent, then the
parent will be raised. The parent window is added to the defer_focus_stack in intercept_raise
callback function.
And finally, the parent window gets the focus by defer_focus policy.

To resolve this problem, we add code that e calls e_client_focus_defer_set for the child window.

Change-Id: I96dd830115213bb93787b1e00fe83e1ca052184c