Specify --max_timestamp when calling brillo_update_payload.

Bug: 36232423
Test: Create OTA packages (full, incremental and downgrade) with
      ota_from_target_files.py; check the parameters passed down to
      brillo_update_payload.
Change-Id: I3af397f05fe16f4a9f0eb73e8272bac6afdc002a
Merged-In: I3af397f05fe16f4a9f0eb73e8272bac6afdc002a
(cherry picked from commit ed08bc4a)