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/welcome/env_test.go b/core/installer/welcome/env_test.go
index ee80e4e..439fdf2 100644
--- a/core/installer/welcome/env_test.go
+++ b/core/installer/welcome/env_test.go
@@ -3,6 +3,7 @@
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"io"
 	"io/fs"
 	"log"
@@ -256,7 +257,13 @@
 	if err := m.m.Add(name, task); err != nil {
 		return err
 	} else {
-		task.OnDone(m.onDone)
+		task.OnDone(func(err error) {
+			if err == nil {
+				m.onDone(nil)
+			} else {
+				m.onDone(fmt.Errorf("%s: %s", name, err))
+			}
+		})
 		return nil
 	}
 }