raft: etcd unit tests: update test_leader_election_overwrite_newer_logs
raft: etcd unit tests: update test_leader_election_overwrite_newer_logs

Make test_leader_election_overwrite_newer_logs use newer communicate()
and other new helpers.

Signed-off-by: Alejo Sanchez <004be06a28e38b437b038f9b5c0b9f5758b792e9@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla