Revert "InCallUI: fix NPE in InCallVibrationHandler"

This reverts commit 42180849741b95d966e011250412d67f60b4d768.
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