veyron2/ipc: allow listen to return multiple endpoints and use verror2.

MultiPart: 1/5

Change-Id: I00446fd7a45a5ed303ea9227c74dce27ba89abb3
diff --git a/tools/profile/impl_test.go b/tools/profile/impl_test.go
index 9569760..e8925e9 100644
--- a/tools/profile/impl_test.go
+++ b/tools/profile/impl_test.go
@@ -89,7 +89,7 @@
 		t.Errorf("NewServer failed: %v", err)
 		return nil, nil, err
 	}
-	endpoint, err := server.Listen(profiles.LocalListenSpec)
+	endpoints, err := server.Listen(profiles.LocalListenSpec)
 	if err != nil {
 		t.Errorf("Listen failed: %v", err)
 		return nil, nil, err
@@ -98,7 +98,7 @@
 		t.Errorf("ServeDispatcher failed: %v", err)
 		return nil, nil, err
 	}
-	return server, endpoint, nil
+	return server, endpoints[0], nil
 }
 
 func stopServer(t *testing.T, server ipc.Server) {