replace some iteritems with six

synapse/handlers/device.py

synapse/handlers/e2e_keys.py

synapse/handlers/groups_local.py

synapse/handlers/presence.py

synapse/handlers/sync.py

synapse/handlers/user_directory.py

synapse/metrics/process_collector.py

synapse/push/bulk_push_rule_evaluator.py

synapse/replication/tcp/protocol.py

synapse/replication/tcp/resource.py

synapse/rest/media/v1/media_repository.py

synapse/storage/client_ips.py

synapse/storage/devices.py

synapse/storage/end_to_end_keys.py

synapse/storage/event_push_actions.py