Use the warnings module to display the git version message.

This allows us to ignore the error:

```python
    warnings.filterwarnings(
        'ignore',
        category=UserWarning,
        module='salt.version'
    )
```
Or, make it raise an exception:

```python
    warnings.filterwarnings(
        'error',
        category=UserWarning,
        module='salt.version'
    )
```
Remove the warnings filter from `salt.version`.
Merge pull request #3285 from s0undt3ch/features/versions-warnings

Use the warnings module to display the git version message.