devstack: Stop setting route pointing back to tenant router
devstack: Stop setting route pointing back to tenant router

The is the networking-odl counter part of devstack patch.
change set of df5e69114fa2af663c50e734b4a842c727e6a7e9
change id of If45e3fc15c050cfbac11b57c1eaf137dd7ed816f
This patch removes both IPv4/IPv6 routes for tenant router
unlike the patch of devstack.

> Stop setting route pointing back to tenant router
>
> This removes the logic to add a route pointing to the IPv4
> tenant private network range since the router is performing
> SNAT. If reaching the IPs via the route worked at all, it was
> by accident since this behavior is certainly not guaranteed
> by Neutron.

Change-Id: Ib4c8b0e1737ce6b2e328dd76b432ac137e1173aa

openstack/networking-odl,openstack/networking-odl,openstack/networking-odl