capi gcp: don't set target pools on machines

CAPG installs will only use backend services--no target pools, so
we need to remove target pools from the machine and control plane
machineset manifests, so the machine-api operator doesn't throw
an error looking for a target pool that doesn't exist.

Author: patrickdillon

pkg/asset/machines/master.go

@@ -265,6 +265,26 @@ func (m *Master) Generate(dependencies asset.Parents) error {
 		if err != nil {
 			return err
 		}
+
+		// CAPG-based installs will use only backend services--no target pools,
+		// so we don't want to include target pools in the control plane machineset.
+		// TODO(padillon): once this feature gate is the default and we are
+		// no longer using Terraform, we can update ConfigMasters not to populate this.
+		if ic.EnabledFeatureGates().Enabled(configv1.FeatureGateClusterAPIInstall) {
+			for _, machine := range machines {
+				providerSpec, ok := machine.Spec.ProviderSpec.Value.Object.(*machinev1beta1.GCPMachineProviderSpec)
+				if !ok {
+					return errors.New("unable to convert ProviderSpec to GCPMachineProviderSpec")
+				}
+				providerSpec.TargetPools = nil
+			}
+			cpms := controlPlaneMachineSet.Spec.Template.OpenShiftMachineV1Beta1Machine.Spec.ProviderSpec.Value.Object
+			providerSpec, ok := cpms.(*machinev1beta1.GCPMachineProviderSpec)
+			if !ok {
+				return errors.New("Unable to set target pools to control plane machine set")
+			}
+			providerSpec.TargetPools = nil
+		}
 	case ibmcloudtypes.Name:
 		subnets := map[string]string{}
 		if len(ic.Platform.IBMCloud.ControlPlaneSubnets) > 0 {