sync: fix sync after re-adding a contact previously removed

If a conversation was previously removed, it couldn't be re-cloned
due to the fact that the sync value can come from a previously
offline device.
Like updateContact in contact_list, use created/removed to determine
if it's a re-added contact to be able to re-sync again.

Change-Id: Ibe16d2bda02cbbe41b16d8b365d9c8ef02b36140