releasetools: Fix the bug in AssertSequenceGood.

We use a bitset for blocks in the target image to assert a block hasn't
been touched before reading. Skip checking the blocks that are in the
source image only.

Bug: 27556903
Change-Id: I3a77292da673c813bd20d8dc177ff36419d8ecae
(cherry picked from commit dca2200c8aa09b08ba0d37410a7826b737caecf2)
1 file changed