AutoPytorch selects only Dummy model.

I run AutoPytorch for 10 hours on a dataset with 1.5 Lac rows and 13 columns, but it was not able to find the model it selects the dummy model.

## Code

```
model = TabularRegressionTask(
ensemble_size=5,
ensemble_nbest=5,
max_models_on_disc=5,
)
model.search(
optimize_metric='r2',
X_train=X_train,
y_train=y_train,
total_walltime_limit=36000,
memory_limit=5092,
enable_traditional_pipeline=False
)

```
## Output
After 10 hours it gives me
```
Dummy Model
```
## Local environment
* Ubuntu
* Python: 3.8
* autopytorch:0.2