Multiple optimizers drops logs
I updated pytorch lightning and that seems to have fixed it. Must have been a specific combination of PTL + NeMo that didn't work. Closing,
**Describe the bug**

With multiple optimizers in the `training_step`, only the final optimizer's logs get printed/logged on the progress bar and in tfevents file. No logged values from the previous optimizers appear on the progress bar or in the tfevents.

**Steps/Code to reproduce bug**

Running examples/tts/melgan.py will show the issue. Only `loss_generator` is logged,  despite in the first optimizer's code `self.log("loss_discriminator", sum_loss_dis, prog_bar=True, sync_dist=True)`


**Expected behavior**

All values logged in the earlier optimizers should persist and be logged.

**Environment overview (please complete the following information)**

 - Environment location: Bare-metal
 - Method of NeMo install: source, current head (1.0.0b4)

**Environment details**

- PyTorch version 1.7
- Python version 3.7
