Recent flakey FV tests

[dnwe]

For a while we had a good run where the FV was stable and rarely failed, but recently there seems to have been an increase in flakiness with a number of tests randomly timing out or failing assertions. Need to investigate what can be done to fixup wherever the holes are

TestFuncTxnProduceWithBrokerFailure occasionally times out (e.g., here)

TestConsumerFetchFollowerFailover occasionally times out (e.g., here)

TestFuncConsumerGroupPartitioningStateful fails assertion "functional_consumer_group_test.go:93: ttl exceeded, expected handlers 5 but got 0" (e.g., here)