fix: right volume_condition message when healthy

[guilhem]

This pull request includes changes to the nodeGetVolumeStats function in the internal/driver/nodeserver_all.go file to improve error handling and volume condition reporting. The most important changes include refactoring the error handling logic and introducing a volumeCondition variable to manage the state of the volume.

Improvements to error handling and volume condition reporting:

• internal/driver/nodeserver_all.go: Introduced a volumeCondition variable to manage the state of the volume, replacing the previous abnormal boolean flag. This change improves the clarity and maintainability of the code.
• internal/driver/nodeserver_all.go: Refactored the error handling logic to use a switch statement for better readability and to handle specific errors (EIO and ENOENT) more explicitly.
• internal/driver/nodeserver_all.go: Updated the response construction to use the new volumeCondition variable, ensuring that the volume condition is accurately reported based on the error encountered.

General:

• [x] Have you removed all sensitive information, including but not limited to access keys and passwords?
• [x] Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

Pull Request Guidelines:

1. [ ] Does your submission pass tests?
2. [ ] Have you added tests?
3. [ ] Are you addressing a single feature in this PR?
4. [ ] Are your commits atomic, addressing one change per commit?
5. [ ] Are you following the conventions of the language?
6. [ ] Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. [ ] Have you explained your rationale for why this feature is needed?
8. [ ] Have you linked your PR to an open issue

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 20 lines in your changes missing coverage. Please review.

Project coverage is 74.51%. Comparing base (4ecf4c4) to head (b20ea31).

Files with missing lines	Patch %	Lines
internal/driver/nodeserver_all.go	0.00%	20 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #311 +/- ## ========================================== - Coverage 74.79% 74.51% -0.28% ========================================== Files 22 22 Lines 2396 2405 +9 ========================================== Hits 1792 1792 - Misses 499 508 +9 Partials 105 105 ```

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