Fix lambda capture

The scheduled takeLayersSnapshotProto() call is not waited anymore
(see deadlock fix for b/313130597), hence the traceFlags local
variable must be captured by value to avoid referencing it after
it goes out of scope.

Fix: 370018409
Flag: EXEMPT bugfix
Test: presubmit
Change-Id: I0285ba70475cec3e4c54787303aea535bf866d72