Goal: When  installconfig.controlPlane.platform.aws.zones is not specified, control plane nodes are correctly placed in the zones considering the zones in the region, balacing correctly in zones (preventing two control plane nodes in same zone, when available in the region).

Bug: in the current installer configuration, when no zones is specified in the control plane compute pool on install-config.yaml, the machine manifest generation is letting[1] capa to decide which zones the control plane is placed, and the default configuration seems to be single zone.

[1] https://github.com/openshift/installer/blob/master/pkg/asset/machines/aws/awsmachines.go#L50