self.log_dict() doesn't support dictionary of Metric objects
🐛 Bug

Calling self.log_dict with a dictionary of Metric object(s) results in 'Trying to pass too many CPU scalars to CUDA kernel!' error. Unlike calling self.log(metric) directly, in this case the internal states are not transferred to device.
Please reproduce using
https://colab.research.google.com/drive/1a7pjASi5_TiSc_XqEFB2Rfd4yaIcFqe2?usp=sharing
Expected behavior
The self.log_dict() method used to work properly with a dictionary of Train/EvalResults objects and is a great solution for tracking multiple metrics in training/validation.
Environment

PyTorch Version (e.g., 1.0): 1.6.0
Pytroch-lightning: 1.0.2
OS (e.g., Linux): Ubuntu 18.04
How you installed PyTorch (conda, pip, source): pip
Python version: 3.6.9
CUDA/cuDNN version: 10.2
GPU models and configuration: 2 x 2080Ti
Any other relevant information: distributed backend: dp, ddp