[mender-binary-delta] disable the checksum verification at the end of the update

Customers requested to disable the end-state checksum calculation in the Mender binary delta update module. The reason is that the checksum calculation requires considerable time and removing it reduces the update time by a 30-35% factor.

According to the client team, the reason why we have such an extra step is to ensure there are no bugs in the xdelta3 library/algorithm. As we never experienced problems (rollbacks), we can assume the check can be safely removed.

Acceptance criteria:

• The end-state checksum calculation is permanently disabled.