FIX #2154 query virtualbox serially

Signed-off-by: David Gageot <david@gageot.net>

commands/ls.go

@@ -306,14 +306,32 @@ func getHostListItems(hostList []*host.Host) []HostListItem {
 	hostListItemsChan := make(chan HostListItem)
 
 	for _, h := range hostList {
-		go getHostState(h, hostListItemsChan)
+		if h.DriverName != "virtualbox" {
+			go getHostState(h, hostListItemsChan)
+		}
 	}
 
-	for range hostList {
-		hostListItems = append(hostListItems, <-hostListItemsChan)
+	// Virtualbox is temperamental about doing things concurrently,
+	// so we schedule the actions in a "queue" to be executed serially
+	// after the concurrent actions are scheduled.
+	for _, h := range hostList {
+		if h.DriverName == "virtualbox" {
+			serialChan := make(chan HostListItem)
+
+			go getHostState(h, serialChan)
+
+			hostListItems = append(hostListItems, <-serialChan)
+			close(serialChan)
+		}
 	}
 
+	for _, h := range hostList {
+		if h.DriverName != "virtualbox" {
+			hostListItems = append(hostListItems, <-hostListItemsChan)
+		}
+	}
 	close(hostListItemsChan)
+
 	return hostListItems
 }