internal/quic/cmd/interop: don't t.Log after test finishes

Fixes golang/go#63971

Change-Id: I795356202880daa2d4a0cfd019c542e5820e8020
Reviewed-on: https://go-review.googlesource.com/c/net/+/539857
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

internal/quic/cmd/interop/main_test.go

@@ -72,9 +72,9 @@ func run(ctx context.Context, t *testing.T, name, testcase string, args []string
 	addrc := make(chan string, 1)
 	donec := make(chan struct{})
 	go func() {
-		defer t.Logf("%v done", name)
 		defer close(addrc)
 		defer close(donec)
+		defer t.Logf("%v done", name)
 		s := bufio.NewScanner(out)
 		for s.Scan() {
 			line := s.Text()