[fr] Support endpoint configuration for cluster-api

[okozachenko1203]

Context

There is an umbrella issue #204
Now cluster-api consumes public endpoints only.
cluster-api is normally installed in the controlplane and many organizations don't allow controlplane egress to internet(public). In this case, cluster-api cannot communicate with openstack api.

Solution

#204 (comment)
Create a new option group [capi_client] in magnum config and configure endpoint type and cert stuff there for capi-controller.