[Openstack][16.1][OVN] - Communication between floating IPs may fail when mulit-subnet provider networks are used

Issue

• This issue is very specific to the following scenarios.
• OVN ML2 neutron plugin is used (default in OSP 16)
• Multiple IPv4 neutron subnets are created on the same provider network.
• The issue can occur when the Neutron routers external IP address is allocated from a different provider subnet than the associated floating IPs.
• This issue only impacts network communication where the source and destination are behind the tenant routers and communicate through the tenant router(s).
• This issue is currently being tracked with this bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1920025