Avoid self-overpping SOURCE_COPY ops by split them am: 58480ef4e5

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1518963

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I9fc737504bd7a2ebaece2c4fa0ab6c87d2f55b58