C: ddb leader isolation: after node rejoin within transaction timout write-transactions returned 500 from all nodes

robot:
https://logs.opendaylight.org/releng/jenkins092/controller-csit-3node-clustering-only-carbon/665/archives/log.html.gz#s1-s50-t1-k2-k18-k1-k1

scenarion:
transactions are produced on each node
the leader is isolated
within few seconds new leader is eleceted (less than 10s)
isolated node is rejoined then and tests waits for shards to be sync on all nodes
write-trancasions rpc should return 200s, but 500s are returned from all nodes

logs https://logs.opendaylight.org/releng/jenkins092/controller-csit-3node-clustering-only-carbon/665/archives/
2017-05-07 18:11:17,081 | INFO | h for user karaf | command | 266 - org.apache.karaf.log.command - 3.0.8 | ROBOT MESSAGE: Starting test Healing_Within_Transaction_Timeout

bug may be related to 8372