Describe the bug
It does't work when replace AsChannelFirstd with EnsureChannelFirstd in deepgrow's dataset.
It mainly due to _save_data_2d only works on the image since EnsureChannelFirstd also makes the label 4-dimensional(with channel 1 at the first).

To Reproduce
python -m unittest test_deepgrow_dataset.py

Traceback (most recent call last):
File "/opt/conda/lib/python3.8/site-packages/parameterized/parameterized.py", line 533, in standalone_func
return func(*(a + p.args), **p.kwargs)
File "/workspace/Code/MONAI/tests/test_deepgrow_dataset.py", line 87, in test_create_dataset
deepgrow_datalist = create_dataset(datalist=datalist, output_dir=self.tempdir, **args)
File "/workspace/Code/MONAI/monai/apps/deepgrow/dataset.py", line 105, in create_dataset
data = _save_data_2d(
File "/workspace/Code/MONAI/monai/apps/deepgrow/dataset.py", line 159, in _save_data_2d
label = vol_label[sid, ...] if vol_label is not None else None
IndexError: index 1 is out of bounds for axis 0 with size 1

(cc @SachidanandAlle @diazandr3s @wyli @Nic-Ma)