Keras example saving optimizer variables for step 0 but not step 10

```
from tests.tensorflow.keras.test_keras import train_model
train_model(
out_dir,
save_all=True,
use_tf_keras=True,
save_config=SaveConfig(save_steps=[0, 10]),
eager=False,
steps=["train", "eval", "predict", "train"],
)
print(create_trial_fast_refresh(out_dir).tensor_names(step=10))
```