BFD Sessions are not established

Reliably

1. We have several ZebOS pods configured with bfd session to cluster node IP.
2. Observe that BFD session in ZebOS was configured properly, but session never established
3. Observe in ovn that some of the BFD sessions were not configured

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Paste from original e-mail thread:

- BFD sessions not showing up on some of our dataplane instances (TMM) and causing these instances to not be used (ingress and egress).

- I think the problem starts with that bfd session was never established with OVN. When we look at imish, we see that the bfd session was never negotiated and OVN never sent us any info on their bfd. 

For example, imish output of bfd session status: 

BFD Session Established:Session Interface Index : 4              Session Index : 9Lower Layer : IPv4                       Version : 1Session Type : Single Hop                Session State : UpLocal Discriminator : 9                  Local Address : 10.144.174.134/32Remote Discriminator : 92881321          Remote Address : 10.144.174.20/32Local Port : 49160                       Remote Port : 3784Options : Diagnostics : None Timers in Milliseconds :Min Tx: 900               Min Rx: 900               Multiplier: 5Neg Tx: 1000              Neg Rx: 1000              Neg detect mult: 5 <<< sent by OVN  

No BFD Session Established:Session Interface Index : 4              Session Index : 7Lower Layer : IPv4                       Version : 1Session Type : Single Hop                Session State : DownLocal Discriminator : 7                  Local Address : 10.144.174.134/32Remote Discriminator : 0                 Remote Address : 10.144.174.18/32Local Port : 49158                       Remote Port : 3784Options : Diagnostics : None Timers in Milliseconds :Min Tx: 900               Min Rx: 900               Multiplier: 5Neg Tx: 0                 Neg Rx: 0                 Neg detect mult: 0 <<< OVN didn't send us anything 

On further inspection, we find that OVN never configured sessions via this command: 
    ovn-nbctl --no-leader-only list bfd 

Manually adding sessions didn't work (we verified with imish commands) 
    ovn-nbctl --no-leader-only create bfd logical_port=rtoe-GR_master-0.ocp7.pd.f5net.com dst_ip=10.144.174.134 min_tx=3000 min_rx=3000 detect_mult=10
    oc exec -it -n rcheng-bz1135533-net f5-tmm-6fcdcdfd8f-dz9nz -c f5-tmm-routing -- imish -e "show bfd session detail" 

Because bfd sessions were never established, session status in imish was DOWN, and so ECMP routes were never added to the OVN Logical Router.