tests.aspects.TestCase.has_site_user: Support '*' as family name
Pywikibot supports '*' as family name since a10cbb30ed58085c754519e066c72d.
Tests that require a username should support this new method of specifying
usernames in userconfig.py and should not be skipped.
Bug: T120334
Change-Id: I278d70127bfc4f8d26035b74c3ae88dda62e37de