Remove .nemo instead of renaming
Docstring needs to be updated but overall ok  added the test from repro: https://github.com/NVIDIA/NeMo/pull/9281/files#diff-b1e596fcfe12238f95a6145a309dfbcdcee6bd67f68505aa42f8865d759f377bR461
also added removing existing .nemo checkpoints in safe way (rename existing, save new, remove old) @titu1994 CI on `main` branch is failing so I added a fix which is unrelated to this PR so that CI passes:
https://github.com/NVIDIA/NeMo/pull/9281/files#diff-efe139cc50f2253e4a5f2b5a268dff86f1094531de824da4067590243be7f928R25 There are some issues with the CI, @pablo-garay can you take a look?

@titu1994 I assume it needs to go to 2.0.0.rc as well? Yup needs to be cherry picked into 2.0 as well 
# What does this PR do ?

This is a fix to #9015 which resulted in creating too many .nemo files.

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