qa/tasks/mgr: partial revert of 'import with full path'

qa/tasks/mgr: partial revert of 'import with full path'

this change partially reverts #34139

using relative import helps with readability and ease the pain to write
down the full parent module name

in #34139, all relative imports were replaced with full path, because we
were using following code to verify if the code is python3 compatible:

```
  mod_spec = importlib.util.spec_from_file_location(mod_name, path)
  mod = importlib.util.module_from_spec(mod_spec)
  mod_spec.loader.exec_module(mod)
```

but this does not work with submodule which can import using relative
import without specifying the name of the package and its parent module.

Signed-off-by: Kefu Chai <kchai@redhat.com>