Fix #818: Decode unexpected octal asterisk in domain name

The Route 53 API returns asterisks as their escaped octal equivalent.
I don't know why, but I asked for help at
https://forums.aws.amazon.com/thread.jspa?threadID=113183 .

This workaround is the approach taken in
https://github.com/fog/fog/issues/1093 and
https://github.com/pcorliss/ruby_route_53/issues/7 .