Fix missing label ops during cow size estimation am: 2931bee8b1

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2166206

Change-Id: I3995fca471089e17a30d0e235c2c3365f31551e8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>