Correctly handle 205 Reset Content response with transfer-encoding

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

codec-http/src/main/java/io/netty/handler/codec/http/HttpObjectDecoder.java

@@ -477,7 +477,7 @@ public abstract class HttpObjectDecoder extends ByteToMessageDecoder {
             }
 
             switch (code) {
-            case 204: case 205: case 304:
+            case 204: case 304:
                 return true;
             }
         }

codec-http/src/test/java/io/netty/handler/codec/http/HttpResponseDecoderTest.java

@@ -368,6 +368,28 @@ public class HttpResponseDecoderTest {
         assertThat(ch.readInbound(), is(nullValue()));
     }
 
+    @Test
+    public void testResetContentResponseWithTransferEncoding() {
+        EmbeddedChannel ch = new EmbeddedChannel(new HttpResponseDecoder());
+        assertTrue(ch.writeInbound(Unpooled.copiedBuffer(
+                "HTTP/1.1 205 Reset Content\r\n" +
+                "Transfer-Encoding: chunked\r\n" +
+                "\r\n" +
+                "0\r\n" +
+                "\r\n",
+                CharsetUtil.US_ASCII)));
+
+        HttpResponse res = ch.readInbound();
+        assertThat(res.protocolVersion(), sameInstance(HttpVersion.HTTP_1_1));
+        assertThat(res.status(), is(HttpResponseStatus.RESET_CONTENT));
+
+        LastHttpContent lastContent = ch.readInbound();
+        assertThat(lastContent.content().isReadable(), is(false));
+        lastContent.release();
+
+        assertThat(ch.finish(), is(false));
+    }
+
     @Test
     public void testLastResponseWithTrailingHeader() {
         EmbeddedChannel ch = new EmbeddedChannel(new HttpResponseDecoder());