improvement(test_default): Extend scylla_args with new flag enable-sstable-key-validation
improvement(test_default): Extend scylla_args with new flag enable-sstable-key-validation

This new flag is an optional flag to detect data corruption issues.
It's supported in master,3.2, 3.3 and 2019.1.6.
We may need to pay attention to performance degredations, stalls or any suspicous slow behaviour.

scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests