SyncStatus stays false for more than 5minutes after bringing 2 of 3 nodes down and back up.

This was seen in a netvirt 3node job:

https://logs.opendaylight.org/releng/jenkins092/netvirt-csit-3node-openstack-ocata-upstream-stateful-carbon/118/log.html.gz

The job has the karaf logs, and in the log for ODL2 I saw this:

2017-09-08 12:43:45,101 | ERROR | Event Dispatcher | AbstractDataStore | 203 - org.opendaylight.controller.sal-distributed-datastore - 1.5.2.SNAPSHOT | Shard leaders failed to settle in 90 seconds, giving up

The system tests were pasing ok until this point, after which a lot
of failures were seen.