fix(tester.py): fix check order for correctness
fix(tester.py): fix check order for correctness

this change was done after PR #3528 was merged,
and this check was left as is. This commit aims
to improve readability and correctness of this
if / else check.

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