--hosts-file-enabled help misleading or default state incorrect

With --help the following description is printed:
```
--hosts-file-enabled
If specified, use hosts files for resolving.
```

1. The hosts files are used _whether this is specified or not_, since in config.go it defaults to true.

2. The syntax to disable the feature is not clear from the help (i.e. --hosts-file-enabled=false)