Fix backwards compatibility issues between CudnnLSTM and LSTMBlockCell. Correct LstmEncoder behavior for variable length sequences. (#1013)
Fix backwards compatibility issues between CudnnLSTM and LSTMBlockCell. Correct LstmEncoder behavior for variable length sequences. (#1013)

* Fix incorrect input to backwards CudnnLSTM in bidi encoder.

* Fix backwards compatibility issues between CudnnLSTM and LSTMBlockCell

* lint

* lint

* lint

* Respond to reviewer.

magenta/magenta,adarob/magenta,magenta/magenta,jesseengel/magenta,jesseengel/magenta,adarob/magenta