Openvswitch SNAT does not work properly when necessary with CISCO aci ml2 driver

Issue

Customer use OSP7 with Cisco ACI /opflex ML2 driver. With this deployment, NAT is done on every Nova Compute, within "br-int" (integration bridge) openvswitch bridge.

When creating an instance and adding a floating IP, connectivity from external networks to floating IP works properly, but after any change on default gateway in any other router that is not related with the previous instance, connectivity from external networks to floating IP assigned is lost.