cli/cmd/cluster-apply.go: don't try to upgrade managed platforms

If we deploy on managed Kubernetes, it won't have controlplane installed
as Helm releases, so we shouldn't try to upgrade it. The upgrade will be
most likely driven by Terraform.

Refs #215 #216

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>

cli/cmd/cluster-apply.go

@@ -84,8 +84,8 @@ func runClusterApply(cmd *cobra.Command, args []string) {
 		ctxLogger.Fatalf("Verify cluster: %v", err)
 	}
 
-	// Do controlplane upgrades only if cluster already exists.
-	if exists {
+	// Do controlplane upgrades only if cluster already exists and it is not a managed platform.
+	if exists && !p.Meta().Managed {
 		fmt.Printf("\nEnsuring that cluster controlplane is up to date.\n")
 
 		cu := controlplaneUpdater{