Controller does not send stats requests to switches after applying a 2 secs delay in the OF channel.

To reproduce:

1) Connect OVS switch to controller.
2) Apply 2 secs RTT delay in the VM running the OVS:

sudo tc qdisc add dev ens3 root handle 1:0 netem delay 2000ms

3) Check with wireshark or in karaf log (DEBUG org.opendaylight.openflowplugin.impl) that controller does not send stats requests to switch.

4) The problem persists even when the delay is removed:

sudo tc qdisc del dev ens3 root