fixing role path sorting in possible_paths list

I changed the order of `possible_paths`list. *Before*, **default** values were first appended then the `DEFAULT_ROLE_PATH` constant. That would cause the next for..in [line 205](https://github.com/ynk/ansible/compare/fix/role_path_order?expand=1#diff-30c8c86d294b2f7b782122bc2eb3e4aeR205) to choose first default, then user-defined role path (and break at first occurence). I think should be reversed, as configuration should be prior to default.