Fix multiprocessing testcase (#7743)
Need to force context re-creating inside testcase otherwise runtime
exception raises:
```
def set_start_method(self, method, force=False):
if self._actual_context is not None and not force:
> raise RuntimeError('context has already been set')
E RuntimeError: context has already been set
```
Command for verification:
`pytest -v tests/unit/runtime/test_ds_initialize.py`
---------
Signed-off-by: Artem Kuzmitckii <artem.kuzmitckii@amd.com>
Co-authored-by: Logan Adams <114770087+loadams@users.noreply.github.com>
