Make it easier to disable bundler checksum by disabling it via false

What does this MR do and why?

Make it easier to disable bundler checksum by disabling it via false

In some places it's more difficult to unset a variable, so this can provide a way to disable it by setting it to false.

Note that every other values will still enable it to keep better compatibility.

The reason why we might want to be able to disable this more easily is explained at: !118938 (comment 1374688877)

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