BUG/MINOR: http: Don't reset the transaction if there are still data to send

To reset an HTTP transaction, we need to be sure all data were sent, for the
request and the response. There are tests on request and response buffers for
that in http_resync_states function. But the return code was wrong. We must
return 0 to wait.

This patch must be backported in 1.7
diff --git a/src/proto_http.c b/src/proto_http.c
index 7141833..e0ed2da 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -5654,16 +5654,18 @@
 		 * and the response buffer must realigned
 		 * (realign is done is http_end_txn_clean_session).
 		 */
-		if (s->req.buf->o)
+		if (s->req.buf->o) {
 			s->req.flags |= CF_WAKE_WRITE;
-		else if (s->res.buf->o)
+			return 0;
+		}
+		else if (s->res.buf->o) {
 			s->res.flags |= CF_WAKE_WRITE;
-		else {
-			s->req.analysers = AN_REQ_FLT_END;
-			s->res.analysers = AN_RES_FLT_END;
-			txn->flags |= TX_WAIT_CLEANUP;
-			return 1;
+			return 0;
 		}
+		s->req.analysers = AN_REQ_FLT_END;
+		s->res.analysers = AN_RES_FLT_END;
+		txn->flags |= TX_WAIT_CLEANUP;
+		return 1;
 	}
 
 	return txn->req.msg_state != old_req_state ||