Notification Widgets : Fix vibration

The initial value of the array determines how long till the vibration starts,
and second value determines how long to leave it on till.

Since config_virtualKeyVibePattern is in an overlay and we cannot rely on its consitency,
we check the length of the array, and based on it execute the appropriate vibration.

Change-Id: Ida88dabc2b3b364501e335bdbe45c84c3845c913