409 in cluster restperfclient test

Recent Carbon snapshot builds. Both only [0] and all [1]. Not seen on 1node job (with non-cluster feature).

Nothing relevant in karaf.log, restperfclient log contains:
07:33:41.121 [pool-4-thread-1] INFO o.o.n.t.t.c.h.p.SyncExecutionStrategy - Begin sending sync requests
07:33:41.489 [pool-4-thread-1] WARN o.o.n.t.t.c.h.p.SyncExecutionStrategy - Status code: 409
07:33:41.490 [pool-4-thread-1] WARN o.o.n.t.t.c.h.p.SyncExecutionStrategy - url: http://10.29.15.75:8181/restconf/config/network-topology:network-topology/topology/topology-netconf/node/17830-sim-device/yang-ext:mount/car:cars
07:33:41.491 [pool-4-thread-1] WARN o.o.n.t.t.c.h.p.SyncExecutionStrategy - <errors xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf"><error><error-type>protocol</error-type><error-tag>data-exists</error-tag><error-message>Data already exists for path: /(urn:opendaylight:params:xml:ns:yang:controller:config:sal-clustering-it:car?revision=2014-08-18)cars/car-entry/car-entry[

{(urn:opendaylight:params:xml:ns:yang:controller:config:sal-clustering-it:car?revision=2014-08-18)id=http://www.example.com/cars/0/2}

]</error-message></error></errors>

[0] https://jenkins.opendaylight.org/releng/view/netconf/job/netconf-csit-3node-periodic-clustering-scale-only-carbon/
[1] https://jenkins.opendaylight.org/releng/view/netconf/job/netconf-csit-3node-periodic-clustering-scale-all-carbon/