testutil, clientv3: wait for panics in txn tests to complete

Fixes #5901

clientv3/txn_test.go

@@ -17,9 +17,13 @@ package clientv3
 import (
 	"testing"
 	"time"
+
+	"github.com/coreos/etcd/pkg/testutil"
 )
 
 func TestTxnPanics(t *testing.T) {
+	defer testutil.AfterTest(t)
+
 	kv := &kv{}
 
 	errc := make(chan string)

pkg/testutil/leak.go

@@ -106,6 +106,7 @@ func interestingGoroutines() (gs []string) {
 		}
 		stack := strings.TrimSpace(sl[1])
 		if stack == "" ||
+			strings.Contains(stack, "runtime/panic.go") ||
 			strings.Contains(stack, "created by testing.RunTests") ||
 			strings.Contains(stack, "testing.Main(") ||
 			strings.Contains(stack, "runtime.goexit") ||