fix(validate_hh_short_downtime): don't run hh nemesis if hinted_handoff is disabled
fix(validate_hh_short_downtime): don't run hh nemesis if hinted_handoff is disabled

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