Don't assume a word has been added to the user dict

The user may now cancel or edit a word upon adding to the
user dictionary. We can no longer assume the word has been
added as is and for the current locale. We should just rely
on standard mechanisms that inform us of new insertions.

Bug: 6015347
Change-Id: I069b19c0c844ca29d6de4c4d162306f9413adea8