fix args share token embeddings in Float16Module
# What does this PR do ?

This PR fixes the args passing problems with Float16Module

**Collection**: [Note which collection this PR will affect]
nlp

# Changelog 
Changing how Float16Module uses share_token_embeddings, if it detects it in the module it should use that and not overwrite it

# Problem fixed
Float16Module ignores the share_token_embeddings flag set by the module because it calls [init](https://github.com/NVIDIA/NeMo/blob/14effd79731ec76a047aefcb3ac4d15c0a7330dd/nemo/collections/nlp/modules/common/megatron/module.py#L262) with no arguments which causes the flag to default to true because MegatronModule sets the default to [True](https://github.com/NVIDIA/NeMo/blob/14effd79731ec76a047aefcb3ac4d15c0a7330dd/nemo/collections/nlp/modules/common/megatron/module.py#L46) which subsequently causes checks like [this](https://github.com/NVIDIA/NeMo/blob/14effd79731ec76a047aefcb3ac4d15c0a7330dd/nemo/collections/nlp/models/language_modeling/megatron_gpt_model.py#L255) to pass despite the user specifying False in the module. Instead Float16Module should inherit this flag from the underlying module whenever possible. 
  
**PR Type**:
- [x] Bugfix
