Proper ssh key file modes and callback usage

[johnnyman727]

This tiny PR does three things:

1. Creates both SSH keys with a 0600 file mode
2. Adds a log that the key generate function worked (if it did)
3. Properly executes callbacks in the key generation function (which was preventing 2 from working)
4. Changes the setupLocal function to call callbacks with function(err) where 'Keys already existcan be an error instead offunction(err, createdBool)`. This method is more consistent with Node.

[johnnyman727]

@Frijol can you give this a quick review?

[Frijol]

lgtm