libsnapshot: Use the compression algorithm specified in the DeltaArchiveManifest.

update_engine and libsnapshot must agree on CowOptions parameters,
otherwise the COW size estimation may be incorrect.

Bug: N/A
Test: vts_libsnapshot_test
      apply OTA, snapshotctl dump
Change-Id: I219ae458dfa19e4b3c96360d3b847edb2a01ebc8