[Jepsen][YCQL] Inconsistency in bank test under partition

[frozenspider]

While running

lein run test --os debian --url ... -w ycql/bank --nemesis partition --time-limit 600 --test-count 1 --concurrency 4n;

using yugabyte/jepsen@875f4ba and YB @ ac17a10, we got 3 failed tests out of 50.
Results of one such run, where banking sum got up from 100 to 102, is attached: 20210318T205628.000Z.zip

[frozenspider]

Regression was introduced by commit 780b4ed

[frozenspider]

Still reproducible after 714a51e: 20210402T162514.000Z.zip

[frozenspider]

Fixed by c9e64df