Fix incidentd stack use-after-return

The detached thread may live longer than the caller, and then "data"
goes out of scope. Fix it by managing data using a strong pointer.

Fixes: 151335416
Test: turn on hwasan, tweak WorkerThreadSection timeout, verify no
hwasan error

Change-Id: I179204b17c381e4e920b9aee07900150d9497639