pytorch-lightning: test fails with `_lazy_train_dataloader`

🐛 Bug

The tests are time-to-time randomly failing across all platforms (but mainly macOS and Win) with following message:

_____________________________ test_lbfgs_cpu_model _____________________________

self = LightningTestModel(
  (c_d1): Linear(in_features=784, out_features=1000, bias=True)
  (c_d1_bn): BatchNorm1d(1000, eps...ats=True)
  (c_d1_drop): Dropout(p=0.2, inplace=False)
  (c_d2): Linear(in_features=1000, out_features=10, bias=True)
)

    def _get_data_loader(self):
        try:
>           value = getattr(self, attr_name)

pytorch_lightning/core/decorators.py:16: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = LightningTestModel(
  (c_d1): Linear(in_features=784, out_features=1000, bias=True)
  (c_d1_bn): BatchNorm1d(1000, eps...ats=True)
  (c_d1_drop): Dropout(p=0.2, inplace=False)
  (c_d2): Linear(in_features=1000, out_features=10, bias=True)
)
name = '_lazy_train_dataloader'

    def __getattr__(self, name):
        if '_parameters' in self.__dict__:
            _parameters = self.__dict__['_parameters']
            if name in _parameters:
                return _parameters[name]
        if '_buffers' in self.__dict__:
            _buffers = self.__dict__['_buffers']
            if name in _buffers:
                return _buffers[name]
        if '_modules' in self.__dict__:
            modules = self.__dict__['_modules']
            if name in modules:
                return modules[name]
        raise AttributeError("'{}' object has no attribute '{}'".format(
>           type(self).__name__, name))
E       AttributeError: 'LightningTestModel' object has no attribute '_lazy_train_dataloader'

To Reproduce

https://github.com/Borda/pytorch-lightning/runs/448238658