* Changes for bfloat16 Zero2

* Cleaned up additional comments and debugging code

* Adapted fp16_master_weights_and_grads option to cover BF16

* Reverted fp16_master_weights_and_gradients extension to BFloat16 and minor cleanup

* Fixed formatting and variable naming errors recognized in testing

* Added relevant unit tests for bfloat16 with ZeRO-2

* Updates conditions for skipping BFloat16 unit tests

* Added check for NCCL inconsistent version naming convention

* Update skip message for Bfloat16 tests to mention additional checks
Co-authored-by: NOlatunji Ruwase <olruwase@microsoft.com>