WandbLogger does not log test results
🐛 Bug
The WandbLogger does not log test results when testing happens right after training.
To Reproduce
When running the MNIST example with the WandbLogger like in the following snippet, the test results do not get logged to wandb because it syncs before testing starts:
Code sample
    ...
    trainer = pl.Trainer(logger=WandbLogger(...))
    trainer.fit(model)
    trainer.test()
Expected behavior
WandbLogger should also log the test results by default like TensorBoardLogger or TestTubeLogger to be a real alternative for the other loggers.
Environment
PyTorch version: 1.4.0
Is debug build: No
CUDA used to build PyTorch: 10.1

OS: Ubuntu 18.04.4 LTS
GCC version: (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0
CMake version: version 3.10.2

Python version: 3.7
Is CUDA available: No
CUDA runtime version: No CUDA
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA

Versions of relevant libraries:
[conda] pytorch-lightning         0.7.1                    pypi_0    pypi
[conda] torch                     1.4.0                    pypi_0    pypi
[conda] torchvision               0.5.0                    pypi_0    pypi