CSIT for VTN Manager failed to test flow filter

The following CSIT for Beryllium VTN Manager occasional failed to test flow filter functions.
https://jenkins.opendaylight.org/releng/view/vtn/job/vtn-csit-1node-manager-all-beryllium/

For example, there was one failure on the build #81.
https://jenkins.opendaylight.org/releng/view/vtn/job/vtn-csit-1node-manager-all-beryllium/81/robot/report/log.html
https://jenkins.opendaylight.org/releng/view/vtn/job/vtn-csit-1node-manager-all-beryllium/81/robot/report/log.html#s1-s1-s3-t19-k1

For example, there was one failure on the build #82.
https://jenkins.opendaylight.org/releng/view/vtn/job/vtn-csit-1node-manager-all-beryllium/82/
https://jenkins.opendaylight.org/releng/view/vtn/job/vtn-csit-1node-manager-all-beryllium/82/robot/report/log.html#s1-s2-s4-t19-k1

The CSIT configures flow filters, and sends packets which match the flow filters.
After that, the CSIT checks if flow entries for the flow filters are correctly created.
However, the CSIT found that the flow entries were not created.