refactor!: server add/rm has better UI/UX

Less confusing logging messages, clear "is created" / "already exists"
output. Move the majority of logging to debug output to not confuse the
situation. Some code cleanups also in there.

pkg/client/client.go

@@ -75,9 +75,9 @@ func New(serverName string) (*client.Client, error) {
 	if info.Swarm.LocalNodeState == "inactive" {
 		if serverName != "default" {
 			return cl, fmt.Errorf("swarm mode not enabled on %s?", serverName)
-		} else {
-			return cl, errors.New("swarm mode not enabled on local server?")
 		}
+
+		return cl, errors.New("swarm mode not enabled on local server?")
 	}
 
 	return cl, nil