CSIT Sporadic failures - no connectivity from control node to instances

L3 connectivity suite

all instances received their dhcp lease

the test cases to ping from the control nodes dhcp namespace to each
instance is failing. However, the connectivity (ping) between instances
across compute nodes is fine. My first suspect was to check the flow
rules on the control node, but I didn't get very far (no time). here
is a direct link to those rules:

https://logs.opendaylight.org/releng/jenkins092/netvirt-csit-1node-openstack-mitaka-upstream-stateful-boron/212/archives/log.html.gz#s1-s1-s2-t9-k3-k1-k1-k1-k16-k4