Description of problem:
Verifying IP Multicast, with receiver and sender VM on two different nodes

Version-Release number of selected component (if applicable):
OSP puddle is:
tag: 16.1_20200930.1
OVN rpm used is:
 ovn2.13-20.06.2-11.el8fdp.x86_64

How reproducible:


Steps to Reproduce:
1. set  NeutronEnableIgmpSnooping: true in THT template.
2. Create a network with vlan on provider network for use with multicast verification.
| provider:network_type     | vlan                                                                                                                                                             |
| provider:physical_network | data2                                                                                                                                                            |
| provider:segmentation_id  | 409   

3.spawn two VMs attached to the above network.
4. Run multicast scenario and script is based on  the redhat solutions ,
https://access.redhat.com/solutions/5165391

multicast receiver:
./multicast.py -I 50.0.3.52 -M 239.0.0.1 -s -p 5405
multicast sender:
 ./multicast.py -I 50.0.3.26 -M 239.0.0.1 hello -p 5405 


Actual results:
When the sender and receiver VMs are on same compute node, receiver is able to get multicast packets.
But when the sender and receiver VMs are on different compute node, receiver is not able to get multicast packets.

Expected results:
sender and receiver VMs are on different compute node, receiver is able to get multicast packets.

Additional info: