Update vagrant sudo syntax

Before:

```
$ sudo -l
Matching Defaults entries for vagrant on flynn:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin

User vagrant may run the following commands on flynn:
    (ALL : ALL) ALL
    (root) NOPASSWD: ALL

$ bash -c "sudo -u nobody date"
[sudo] password for vagrant: 
```

After:

```
$ sudo -l
Matching Defaults entries for vagrant on flynn:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin

User vagrant may run the following commands on flynn:
    (ALL : ALL) ALL
    (ALL) NOPASSWD: ALL

$ bash -c "sudo -u nobody date"
Sun Aug 10 18:07:12 UTC 2014
```