Motivation:
According to RFC 7231 the server may choose to:
```
indicate a zero-length payload for the response by including a
Transfer-Encoding header field with a value of chunked and a message
body consisting of a single chunk of zero-length
```
https://tools.ietf.org/html/rfc7231#page-53
In such cases the exception below appears during decoding phase:
```
java.lang.IllegalArgumentException: invalid version format: 0
at io.netty.handler.codec.http.HttpVersion.<init>(HttpVersion.java:121)
at io.netty.handler.codec.http.HttpVersion.valueOf(HttpVersion.java:76)
at io.netty.handler.codec.http.HttpResponseDecoder.createMessage(HttpResponseDecoder.java:118)
at io.netty.handler.codec.http.HttpObjectDecoder.decode(HttpObjectDecoder.java:219)
```
Modifications:
HttpObjectDecoder.isContentAlwaysEmpty specifies content NOT empty
when 205 Reset Content response
Result:
There is no `IllegalArgumentException: invalid version format: 0`
when handling 205 Reset Content response with transfer-encoding
72a216625f