libsnapshot: Fix vts_libsnapshot_test.SnapshotUpdateTest#FullUpdateFlow am: 29971711 am: 43272903 am: 355141f9

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/core/+/19263115



Change-Id: I3780e50a9369d228397038ca237d324ab3332e9c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>