Add WRITE_TO_PARCEL reference before creash snapshot starting window.

If the snapshot object represents Home task, the snapshot could be
removed before create snapshot starting window, add a reference to keep
it alive before passing to Shell.

Flag: com.android.window.flags.release_snapshot_aggressively
Bug: 398521360
Test: 1. set credential.
2. open MinusOneActivity, then screen off
3. Unlock device with NO_ANIMATION(ref issue description)

Change-Id: Iaab5a3c3f68791aed769dfa3daa0e1cfc4023e25