Revert "InCallUI: fix NPE in InCallVibrationHandler"

This reverts commit df4ca97e270916ccd734c9382e7fb98c019e9c58.
Fix call tracking.

getActiveCall() can return null when ending calls locally before they
are answered locally, so better use the presence of an active call as
indicator of whether to do the vibration instead of using the state.

Change-Id: I088cd743c9a9e6704e93f8c48fb566b3a20ca8be