Fixed stack overflow when editing contact with two deceased people

I saw the stack overflow error a couple more times on Errbit when someone edited a deceased person, and I ran into it again with the Google sync. This is take 2 of my fix for it which hopefully resolves the problem. I switch to directly call `update_columns` rather than `save` for the associated contact to avoid a potential for the `before_save` recursion hook. I also added logic to leave a single deceased person's `greeting` and associated contact `name` to be the same.
Prefer a positive over a double negative:
`next if contact_updates == {}`