Do not force notification vibrations in Vibrate Mode

If apps set DEFAULT_VIBRATE flag for their notifications,
then even if the user has disabled vibrations for the app
in the app configuration settings (such as Hangouts),
then vibrations would still occur. Even after disabling
the "Vibrate on notification" setting in Settings > Sound.

This patch will respect the users choice on whether to
vibrate, based on what they have the "Vibrate on
notification" set to.

Change-Id: If458c461eb87099be08103b5e21518856c16903a
Signed-off-by: Roman Birg <roman@cyngn.com>