Add fixme related to timeout/heartbeat issue

Signed-off-by: Alexandre Beslic <abronan@docker.com>

cli/cli.go

@@ -82,6 +82,7 @@ func Run() {
 					log.Fatalf("discovery required to list a cluster. See '%s list --help'.", c.App.Name)
 				}
 
+				// FIXME Add and use separate timeout flag instead of forcing it
 				d, err := discovery.New(dflag, 10)
 				if err != nil {
 					log.Fatal(err)