Comment 19 for bug 1567668

UPD: We introduced this bug by switching from ovs2.0 to ovs2.5 as with former version probe wasn't used for ptcp connections: https://github.com/openvswitch/ovs/commit/f5cd74291d02f3723e175048db87b2914cd99e34

With probes and busy server, greenthread that processes echo requests from server might not get processed in time. Which means that server disconnects after not getting echo reply.