l2switch does not push flood flows to single switch

Issue is tracked here

https://jenkins.opendaylight.org/releng/view/l2switch/job/l2switch-csit-1node-periodic-host-scalability-daily-only-boron/plot/Inventory%20Host%20Scalability/

To reproduce:

1) bring mininet with single switch and 2 hosts:

udo mn --controller=remote,ip=192.168.0.1 --topo linear,1,2 --switch ovsk,protocols=OpenFlow13

2) Check flows:

mininet> dpctl dump-flows -O OpenFlow13

• • • s1 ------------------------------------------------------------------------
      OFPST_FLOW reply (OF1.3) (xid=0x2):
      cookie=0x2b00000000000032, duration=5.775s, table=0, n_packets=0, n_bytes=0, priority=100,dl_type=0x88cc actions=CONTROLLER:65535
      cookie=0x2b00000000000032, duration=5.776s, table=0, n_packets=14, n_bytes=1176, priority=0 actions=drop

Without flood flows no host is discovered.