Show which sh is calling us. Thanks @techhat!

Example output:
```
$ sudo /bin/bash /salt/source/bootstrap-salt-minion.sh
 * INFO: /bin/bash /salt/source/bootstrap-salt-minion.sh -- Version 1.2
$ sudo bash /salt/source/bootstrap-salt-minion.sh
 * INFO: bash /salt/source/bootstrap-salt-minion.sh -- Version 1.2
$ sudo /salt/source/bootstrap-salt-minion.sh
 * INFO: /bin/sh /salt/source/bootstrap-salt-minion.sh -- Version 1.2
```