Dedupe vibrator state in SystemVibrator callbacks

Add check for state change in SystemVibrator implementation for
OnVibratorStateChangedListener callbacks on devices with more than one
vibrator. The registered listener should be notified only once for
each state when any vibrator starts or stops vibrating.

Fix: 249727855
Test: android.os.VibratorTest
Change-Id: Ied46ad70186a2df1c7aa24ccf04e5e8e05824876