Skip SOURCE_COPY with same src/dst extent am: 47c7d7f50c am: 80cab7e336

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Id4e8eb6816011cb589944799910aa880ea46d19c