ovn-controller: Refactor conntrack zone allocation.
We currently allocate conntrack zones in binding.c. It fits
in nicely there because we currently only allocate conntrack
zones to logical ports and binding.c is where we figure out
the local ones.
An upcoming commit needs conntrack zone allocation for routers
in a gateway. For that reason, this commit moves conntrack zone
allocation code to ovn-controller.c where it would be easily
accessible for router zone allocation too.
Signed-off-by: Gurucharan Shetty <guru@ovn.org>
Acked-by: Ben Pfaff <blp@ovn.org>