clone: use "official" API to create local clone destination This make sure we have a properly created, fully functional repository early. This will be useful to simply the hardlink/copy phases of the local clone to make it share more of its logic with the similar "stream" cloning. This has a minor impact of the test and the resulting repository has is better initialized (eg: the `wcache` directory is pre-created.) Differential Revision: https://phab.mercurial-scm.org/D10850