[CaaS] docs vs sunbeam enable caas

[Matt Verran]

Problem: Just noticed that if you follow https://microstack.run/docs/caas as is then it references Octavia/Loadbalancer. If you simply 'sunbeam enable caas' then you'll hit an error as it doesn't enable it (although it does enable heat, vault etc).

Mitigation: manually enable loadbalancer.

Resolution: One of the following:-

1) change the docs to add that step in.
2) sunbeam enable caas should enable loadbalancer as well