Skip SOURCE_COPY with same src/dst extent am: 47c7d7f50c

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1521718

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I30db6e0a1be98c9d6730d8c7f34fa3450464aeb4