data inconsistency after adding indexes with multi-schema optimization in partition table

[wjhuang2016]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

func TestMultiSchemaAddIndexMerge(t *testing.T) {
	store := testkit.CreateMockStore(t)
	defer ingesttestutil.InjectMockBackendMgr(t, store)()
	tk := testkit.NewTestKit(t, store)
	tk.MustExec("use test")
	tk2 := testkit.NewTestKit(t, store)
	tk2.MustExec("use test")

	tk.MustExec("create table t (a int, b int) PARTITION BY HASH (`a`) PARTITIONS 4;")
	tk.MustExec("insert into t values (1, 1), (2, 2), (3, 3);")

	first := true
	var tk2Err error
	ingest.MockExecAfterWriteRow = func() {
		if !first {
			return
		}
		_, tk2Err = tk2.Exec("insert into t values (4, 4), (5, 5);")
		first = false
	}

	tk.MustExec("alter table t add index idx1(a), add index idx2(b);")
	require.False(t, first)
	require.NoError(t, tk2Err)
	tk.MustExec("admin check table t;")
}

2. What did you expect to see? (Required)

Test pass

3. What did you see instead (Required)

Messages:   	sql:admin check table t;, [], error stack [admin:8223]data inconsistency in table: t, index: idx2, handle: 5, index-values:"" != record-values:"handle: 5, values: [KindInt64 5]"

4. What is your TiDB version? (Required)

master