Register for fallback vibration's death

If we don't link the fallback vibration's death then when we go to
unlink the vibration when it's done we crash with a NoSuchElement
exception. This way if the process that sent us the vibration dies then
the vibration also stops.

Bug: 73134668
Test: Trigger fallback vibration, doesn't crash
Change-Id: I8d8987773eaf45d7989ae46305a9f1558a73c5da