ClusterManager: Implements support of remote clusters.

After this change users will be able to:
* Create cluster and add/remove servers to it
* Install apps on remote cluster
* Move already installed apps between clusters
* Apps running on server being removed will auto-migrate
  to another server from that same cluster

This is achieved by:
* Installing and running minimal version of dodo on remote cluster
* Ingress-nginx is installed automatically on new clusters
* Next to nginx we run VPN client in the same pod, so that
  default cluster can establish secure communication with it
* Multiple reverse proxies are configured to get to the
  remote cluster service from ingress installed on default cluster.

Next steps:
* Support remote clusters in dodo apps (prototype ready)
* Clean up old cluster when moving app to the new one. Currently
  old cluster keeps running app pods even though no ingress can
  reach it anymore.

Change-Id: Iffc908c93416d4126a8e1c2832eae7b659cb8044
diff --git a/core/installer/helm.go b/core/installer/helm.go
index 7d3c334..dc742d5 100644
--- a/core/installer/helm.go
+++ b/core/installer/helm.go
@@ -100,7 +100,7 @@
 	if err != nil {
 		return err
 	}
-	if err := rfs.RemoveDir(root); err != nil {
+	if err := rfs.RemoveAll(root); err != nil {
 		return err
 	}
 	return util.Walk(wtFS, "/", func(path string, info fs.FileInfo, err error) error {