Review comments.

Signed-off-by: Steve Simpson <[email protected]>

Author: stevesg

integration/integration_memberlist_single_binary_test.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/cortexproject/cortex/integration/ca"
 	"github.com/cortexproject/cortex/integration/e2e"
@@ -167,7 +168,7 @@ func TestSingleBinaryWithMemberlistScaling(t *testing.T) {
 		name := fmt.Sprintf("cortex-%d", i+1)
 		join := ""
 		if i > 0 {
-			join = fmt.Sprintf("%s-cortex-1:8000", networkName)
+			join = e2e.NetworkContainerHostPort(networkName, "cortex-1", 8000)
 		}
 		c := newSingleBinary(name, "", join)
 		require.NoError(t, s.StartAndWaitReady(c))
@@ -183,11 +184,14 @@ func TestSingleBinaryWithMemberlistScaling(t *testing.T) {
 
 	// Scale down as fast as possible but cleanly, in order to send out tombstones.
 
+	stop := errgroup.Group{}
 	for len(instances) > minCortex {
 		i := len(instances) - 1
-		require.NoError(t, s.Stop(instances[i]))
+		c := instances[i]
 		instances = instances[:i]
+		stop.Go(func() error { return s.Stop(c) })
 	}
+	require.NoError(t, stop.Wait())
 
 	// If all is working as expected, then tombstones should have propagated easily within this time period.
 	// The logging is mildly spammy, but it has proven extremely useful for debugging convergence cases.