Decode unexpected octal asterisk in domain name

The Route 53 API returns asterisks as their escaped octal equivalent.
[I don't know why](https://forums.aws.amazon.com/thread.jspa?threadID=113183).

This workaround is the approach taken in
[fog #1093](https://github.com/fog/fog/issues/1093)
and [ruby_route_53 #7](https://github.com/pcorliss/ruby_route_53/issues/7).