L3 router interface not being installed in nodes in specific cases

In the scenario where:

1)router interface is created, but there are no tenants in a certain node;
2)followed by the creation of a tenant instance in the given node.

The flows associated with the router interface are not being populated in
the node. A logic is missing so that nodes can install the router interfaces
as soon as the first tenant is created.

Note that the converse is working properly: if tenants are created prior to
the router interface, the flows for the router interface get installed. But
that is unlikely the sequence by with create will follow. The implementation
must work, independent of the order.