Issue #50712 - Version comparison doesn't work correctly on git builds
Bug Description:
```
>>> get_ds_version()
'1.4.2.3.20191112git7a7bc7872'
>>> ds_is_older('1.4.0')
True
```
This happens because packaging.version returns a different object for
'1.4.2.3.20191112git7a7bc7872' (LegacyVersion) than for '1.4.0'
(Version).
And during comparison Version is always higher:
```
>>> x = Version('1.0')
>>> y = LegacyVersion('2.0')
>>> x > y
True
```
Fix Description:
Always use LegacyVersion during comparison
Fixes: https://pagure.io/389-ds-base/issue/50712
Reviewed by: tbordaz (Thanks!)