Tiny typo in tab completion.

**policy access-list tab completion looks like this**

```
vyatta@r1-part# set policy access-list 10 rule <tab><tab> 
Possible completions:
 > <1-65535>>   Access-list rule number
 > 10
```

**It should/could look like access-list6 tab completion:**

```
vyatta@r1-part# set policy access-list6 test rule <tab><tab>
Possible completions:
 > <1-65535>    Access-list6 rule number
```