Fix CPU Initialization and TP>1 for LoRA Merge Script
jenkins jenkins LGTM! jenkins
# What does this PR do ?

Fix 1) merging on CPU, in cases where a GPU is not available, and 2) merging a LoRA model trained with TP>1 into a base model in the distributed checkpointing format.

Tested on Llama2-7b + TP {1, 2, 4} LoRA ckpt, with cpu and gpu options

# Usage

Merging on GPU/CPU can be controlled by
`trainer.accelerator='cpu' | 'gpu'`

Also, the script should always be run with 
`trainer.devices=1` now for distributed checkpoints. If the model cannot fit into one GPU, use the CPU option.


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