Fix file descriptor leak on IncFS v1 am: 4d2d129f2b

Original change: https://android-review.googlesource.com/c/platform/system/incremental_delivery/+/2289234

Change-Id: I559a62777b571cbec6f5fee972ffa96e8c5c6865
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>