JVMCBC-151: fix broken query keepAlive

Motivation
----------
In QueryHandler, keepalive is broken: it is marked as finishedDecoding
too soon, not taking into account that the first response could not be
a LastHttpComponent. This can break the handling of query requests.

Modifications
-------------
Only finish the decoding and issue the response for keepalive when we
received a LastHttpComponent.

Results
-------
Keepalive doesn't interfere with query handling anymore.

Change-Id: I445f86596e629e1d0874f4606978e50019b09666
Reviewed-on: http://review.couchbase.org/46943
Tested-by: Simon Baslé <simon@couchbase.com>
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>

src/main/java/com/couchbase/client/core/endpoint/query/QueryHandler.java

@@ -192,10 +192,12 @@ protected CouchbaseResponse decodeResponse(final ChannelHandlerContext ctx, fina
         }
 
         if (currentRequest() instanceof KeepAliveRequest) {
-            response = new KeepAliveResponse(statusFromCode(responseHeader.getStatus().code()), currentRequest());
-            responseContent.clear();
-            responseContent.discardReadBytes();
-            finishedDecoding();
+            if (msg instanceof LastHttpContent) {
+                response = new KeepAliveResponse(statusFromCode(responseHeader.getStatus().code()), currentRequest());
+                responseContent.clear();
+                responseContent.discardReadBytes();
+                finishedDecoding();
+            }
         } else if (msg instanceof HttpContent) {
             responseContent.writeBytes(((HttpContent) msg).content());
             boolean lastChunk = msg instanceof LastHttpContent;