remove binstub before create

`create_file` method provides by Thor asks overwrite policy when file already exist.

```
-----> Starting Kitchen (v1.1.1)
-----> Setting up <ipfilter-sm-base64>...
-----> Setting up Busser
       Creating BUSSER_ROOT in /tmp/busser
       Creating busser binstub
Overwrite /tmp/busser/bin/busser? (enter "h" for help) [Ynaqdh]
```