Missing tests for liquidation cancellation

[gkaracha]

Due to the specific conditions needed for the cancellation of a liquidation, we currently have no test where Checker.entrypoint_cancel_liquidation_slice succeeds in returning a liquidation slice back to its burrow. Now that it's been getting easier to write e2e tests it's probably time to add tests for more intricate scenaria where cancellation is possible.

[dorranh]

@gkaracha, would you consider this issue resolved after #193, or would you prefer that we add additional tests for this case?

[gkaracha]

@dorranh As far as the e2e tests are concerned I do consider it resolved indeed! I would still like us to be able to expand our tests on the OCaml side though (see discussion with @utdemir here: #195 (review)). We could resolve this issue and open another one, though I think I'd just leave this one open instead.