message: [tf.data / Bigtable]: Set AlwaysRetryMutationPolicy
  Because the tf.data integration currently doesn't support setting client-side timestamps, using the AlwaysRetryMutationPolicy can make data loading more reliable. (This is safe-ish to do, because when reading TF always read Latest(1), so duplicate writes will not be visible to user programs.)
diff: @@ -58,7 +58,8 @@ class BigtableTableResource : public ResourceBase {
  BigtableTableResource(BigtableClientResource* client, string table_name)
  : client_(client),
  table_name_(std::move(table_name)),
  - table_(client->get_client(), table_name_) {
  + table_(client->get_client(), table_name_,
  + google::cloud::bigtable::AlwaysRetryMutationPolicy()) {
  client_->Ref();
  }
  