entry: fix cursor position initialization issues when theme is changed

entry: fix cursor position initialization issues when theme is changed

The issue was caused by the following patch.
"elm_entry: Save cursor position before entry text clear"

It needed to get cursor position at the text_set function to avoid
cursor position issue by delaying signal callback functions.
So, we can't remove the patch. In the theme_apply, we need to handle
cursor position more carefully to fix this side effect.

@tizen_fix

Change-Id: Id63aa401ba2572559bc241f54350b781c72f5092