Change the way notifications work for non-default KitKat.

Messages that are not "secure" (encrypted or key exchange) are
automatically marked as read if TextSecure isn't the default
KitKat SMS app.

This change in functionality allows people who aren't using
TextSecure as a default SMS app on KitKat to still receive
notifications when they get incoming encrypted messages.
Fix for bug that could drop unencrypted MMS on KitKat.