OpenTSDB: Isolated netty channel from the HttpQuery class. (https://rbcommons.com/s/pepperdata/r/3453)
- Factored out the methods we need from the netty Channel to IoChannel and
IoChannelFuture interfaces. - Wrapped the netty Channel and ChannelFuture in
NettyIoChannel and NettyIoChannelFuture classes. - We need it to run background
queries without HTTP connection.