Fix hang with large COM_STMT_SEND_LONG_DATA

The router did not take large packets into account when determining
whether the server will respond. This caused the response counts to be off
by one for all large packets.

server/modules/routing/readwritesplit/rwsplit_route_stmt.cc

@@ -965,7 +965,7 @@ bool RWSplitSession::handle_got_target(GWBUF* querybuf, SRWBackend& target, bool
     }
 
     if (m_qc.load_data_state() != QueryClassifier::LOAD_DATA_ACTIVE &&
-        mxs_mysql_command_will_respond(cmd))
+        !m_qc.large_query() && mxs_mysql_command_will_respond(cmd))
     {
         response = mxs::Backend::EXPECT_RESPONSE;
     }