Fix race in combined iterator test (#183)

The fetchers may not have started right after the iterator is created.
Interrupt after snapshotter has started.

source/logrepl/combined_test.go

@@ -165,16 +165,6 @@ func TestCombinedIterator_Next(t *testing.T) {
 
  expectedRecords := testRecords()
 
- // interrupt repl connection
- var terminated bool
- is.NoErr(pool.QueryRow(ctx, fmt.Sprintf(
- `SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE
- query ILIKE '%%CREATE_REPLICATION_SLOT %s%%' and pid <> pg_backend_pid()
- `,
- table,
- )).Scan(&terminated))
- is.True(terminated)
-
  // compare snapshot
  for id := 1; id < 5; id++ {
  t.Run(fmt.Sprint("next_snapshot", id), func(t *testing.T) {
@@ -194,6 +184,16 @@ func TestCombinedIterator_Next(t *testing.T) {
  })
  }
 
+ // interrupt repl connection
+ var terminated bool
+ is.NoErr(pool.QueryRow(ctx, fmt.Sprintf(
+ `SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE
+ query ILIKE '%%CREATE_REPLICATION_SLOT %s%%' and pid <> pg_backend_pid()
+ `,
+ table,
+ )).Scan(&terminated))
+ is.True(terminated)
+
  t.Run("next_cdc_5", func(t *testing.T) {
  is := is.New(t)