CASSANDRA-21177- Adding option for randomizing memtable type in Simulator tests

[shruti-p-s]

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The Cassandra Jira

[maedhroz]

CI: https://ci-cassandra.apache.org/view/patches/job/Cassandra-devbranch-5/421/

[maedhroz]

I think we need to retain this catch block. It handles errors from try (ClusterSimulation<?> cluster = factory.create(currentSeed)) right?