[Disk Manager] fix idempotence of sync deletion of non-existent disk (#5157)

If we delete non-existent disk twice using `sync` flag, then the second
deletions ends with an error:

```
    disk_service_test.go:1275: 
                Error Trace:    /-S/cloud/disk_manager/internal/pkg/facade/disk_service_test/disk_service_test.go:1275
                                                        /-S/cloud/disk_manager/internal/pkg/facade/disk_service_test/disk_service_test.go:1285
                Error:          Received unexpected error:
                                rpc error: code = Unknown desc = Non retriable error, Silent=false: unknown zone "", available zones: ["zone-a" "zone-b" "zone-c" "no_dataplane" "zone-d" "zone-d-shard1"]
```

Errors occures here, in `setEstimate`:
https://github.com/ydb-platform/nbs/blob/main/cloud/disk_manager/internal/pkg/services/disks/delete_disk_task.go#L216

- After the first deletion tombstone is insterted into the database
- On the second deletion, we call GetDiskMeta here
https://github.com/ydb-platform/nbs/blob/main/cloud/disk_manager/internal/pkg/services/disks/delete_disk_task.go#L206
and get a tombstone.
- The tombstone has empty zone id, so we can't create a Blockstore
client with empty zone.

Author: gy2411

cloud/disk_manager/internal/pkg/facade/disk_service_test/disk_service_test.go

@@ -1218,3 +1218,48 @@ func TestDiskServiceShouldCreateSsdNonreplWithRootKmsEncryptionByFolderID(
 		nil, // encryptionDesc
 	)
 }
+
+func testDiskServiceDeleteNonExistentDisk(t *testing.T, sync bool) {
+	ctx := testcommon.NewContext()
+
+	client, err := testcommon.NewClient(ctx)
+	require.NoError(t, err)
+	defer client.Close()
+
+	diskID := t.Name() + "_NonExistent"
+
+	reqCtx := testcommon.GetRequestContext(t, ctx)
+	operation, err := client.DeleteDisk(reqCtx, &disk_manager.DeleteDiskRequest{
+		DiskId: &disk_manager.DiskId{
+			DiskId: diskID,
+		},
+		Sync: sync,
+	})
+	require.NoError(t, err)
+	require.NotEmpty(t, operation)
+	err = internal_client.WaitOperation(ctx, client, operation.Id)
+	require.NoError(t, err)
+
+	// Should be idempotent.
+	reqCtx = testcommon.GetRequestContext(t, ctx)
+	operation, err = client.DeleteDisk(reqCtx, &disk_manager.DeleteDiskRequest{
+		DiskId: &disk_manager.DiskId{
+			DiskId: diskID,
+		},
+		Sync: sync,
+	})
+	require.NoError(t, err)
+	require.NotEmpty(t, operation)
+	err = internal_client.WaitOperation(ctx, client, operation.Id)
+	require.NoError(t, err)
+
+	testcommon.CheckConsistency(t, ctx)
+}
+
+func TestDiskServiceDeleteNonExistentDisk(t *testing.T) {
+	testDiskServiceDeleteNonExistentDisk(t, false /* sync */)
+}
+
+func TestDiskServiceDeleteNonExistentDiskSync(t *testing.T) {
+	testDiskServiceDeleteNonExistentDisk(t, true /* sync */)
+}

cloud/disk_manager/internal/pkg/services/disks/delete_disk_task.go

@@ -208,7 +208,7 @@ func (t *deleteDiskTask) setEstimate(
 		return err
 	}
 
-	if diskMeta == nil {
+	if diskMeta == nil || len(diskMeta.ZoneID) == 0 {
 		// Should be idempotent.
 		return nil
 	}