Fixed #7153 -- _resolve_lookup now does a better job of resolving callables...

Fixed #7153 -- _resolve_lookup now does a better job of resolving callables and correctly catches all silent_variable_exceptions

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14992 bcc190cf-cafb-0310-a4f2-bffc1f526a37