DEFAULT_VIBRATE must always use the default vibe pattern

The logic here was backwards, causing the (softer) fallback vibe
pattern to be applied if the notification specified a sound
(or DEFAULT_SOUND) and also DEFAULT_VIBRATE. The fallback
vibe should only play if you have *no* vibration set.

Bug: 7588655
Change-Id: Iecdd362729bccedf779b51cc9b90a12014328aff