Description of problem:

I've been hitting some issues lately related to the overcloud getting deployed with the default tenant network, router and external network that made me think it would be better to get the overcloud deployed without them.

1. The openstack overcloud deploy command always creates a default-net tenant network, a router and an ext-net external network. While this is good for demo purposes I believe they are not needed in a production environment for naming or functional reasons and first thing that an operator does is to delete them.

2. You might not need the default router. For instance I'd like to test vlan provider networks but the deploy command ends with the ext-net network and default router created which I don't need.

3. It generates confusion when using network isolation. You have to specify --floating-ip-cidr --floating-ip-start --floating-ip-end --bm-network-gateway that match the external network settings set up in the network isolation yaml file in order to get working connectivity. If you end up deleting them right after deployment finishes then you get a very long deploy command for nothing which leads to bad user experience.

I believe we should leave the creation of routers and networks as a post deployment step so operators can create those according to their particular needs. Or at least get a flag to the deploy command where we can specify if we want them created.