Fixes the mbuf allocation not initialized problem. This problem will cause
the mbufs not be able to freed back to mempool by rte_pktmbuf_free().
Fixes: ef3403fb6f9a ("port: source and sink")
Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>