bugfix: Do not report NVM loaded when not loaded

[urda]

Pull Request Checklist

This is a bugfix release. _urdabash_version_check would incorrectly report nvm loaded status.

• bashrc

  • Only set URDABASH_LOADED_NVM if nvm.
  • Only export NVM_DIR if nvm is actually loaded.

• Are you the repo owner? urda.bash is not accepting outside pull requests at this time.

• Did you update URDABASH_VERSION in bashrc? In VERSION?

• Did make test pass?

• Do all files have headers?

• Did make copy get updated (if required)?

• Did make diffs get updated (if required)?

• Did make test get updated (if required)?