Commit d572632f3d added support in build
system to blacklist given vendor properties. When
ro.vendor.build.fingerprint gets blacklisted, the OTA generation script
can't rely on those properties to determine a change in vendor images.
This CL considers such a case as "vendor images must have changed"
between the two builds.
Bug: 113892939
Test: Generate an incremental package with builds not having
ro.vendor.build.fingerprint.
Test: python -m unittest test_ota_from_target_files
Change-Id: I188de9c3cbeecf26132c92b9356e9d5fef75205e
ea6cbd0765