efl_ui_focus_manager_calc: invalidate obj on delete.

efl_ui_focus_manager_calc: invalidate obj on delete.

Summary:
In some situations focus is being set to a deleted object.
Use EFL_EVENT_INVALIDATE on object deletion not
EFL_EVENT_DEL. This prevents the object to be again selected for restoring focus when a redirect is deleted.

This fixes SEGV with some widgets including popup tests.

Test Plan:
* elementary_test -to popup
* popup-center-text + 3 button (check add, remove buttons).
* Close popup, enter text (reopen popup and repeat).
* Crash should be avoided.

Reviewers: bu5hm4n, zmike

Reviewed By: bu5hm4n

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7026