Append enabled_option

With this option, I can disable sshfs auto start.

Next, I will append a new command : 

```
vagrant sshfs
```

Why this need ? I my project I need to mount some folder. This folder didn't exists before Ansible provisioning.

My workflow : 

* vagrant up (provisioning is executed)
* vagrant sshfs (now I can mount folder because provisioning have create its)