nightly tests: test_efficientnet

[wyli]

Describe the bug
looks like an error for unstable network connections:

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ERROR: test_kitty_pretrained_2 (tests.test_efficientnet.TestEFFICIENTNET)
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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 "/tmp/tmp.jKoFOEwLkl/tests/test_efficientnet.py", line 316, in test_kitty_pretrained
    net = test_pretrained_networks(EfficientNetBN, input_param, device)
  File "/tmp/tmp.jKoFOEwLkl/tests/utils.py", line 97, in test_pretrained_networks
    return network(**input_param).to(device)
  File "/opt/conda/lib/python3.8/site-packages/monai/networks/nets/efficientnet.py", line 556, in __init__
    _load_state_dict(self, model_name, progress, adv_prop)
  File "/opt/conda/lib/python3.8/site-packages/monai/networks/nets/efficientnet.py", line 719, in _load_state_dict
    pretrain_state_dict = model_zoo.load_url(model_url, progress=progress)
  File "/opt/conda/lib/python3.8/site-packages/torch/hub.py", line 590, in load_state_dict_from_url
    return torch.load(cached_file, map_location=map_location)
  File "/opt/conda/lib/python3.8/site-packages/torch/serialization.py", line 608, in load
    return _legacy_load(opened_file, map_location, pickle_module, **pickle_load_args)
  File "/opt/conda/lib/python3.8/site-packages/torch/serialization.py", line 794, in _legacy_load
    deserialized_objects[key]._set_from_file(f, offset, f_should_read_directly)
RuntimeError: unexpected EOF, expected 161000 more bytes. The file might be corrupted.

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