Log failures to unlinkToDeath wakelocks.

Some wakelocks are throwing an exception when unlinking. This should be
impossible, so start catching and logging failures as WTFs so they get
uploaded when it happens again.

Fixes: 182841946
Bug: 180891878
Test: N/A
Change-Id: I9e7a0aa745852178cbfd793451e150e34e7b5488