LR scheduler unit tests (#429)
* Add Linear warmup+decay lr schedule
Update lr schedule unit tests
* LR scheduler unit tests for LR Range Test and 1Cycle
* Disable yapf to preserve parameterizaton
* Disable test_pipe.py for CI debugging
* Disable test_lr_scheduler for CI debugging
* Disable test_lr_scheduler for CI debugging
* Enable all unit tests for CI debugging
Co-authored-by: Jeff Rasley <jerasley@microsoft.com>
