With this patch it is possible to connect 2 DPDK memifs into loopback,
i.e. when they have the same id and different roles, as for example:
"--vdev=net_memif0,role=master,id=0"
"--vdev=net_memif1,role=slave,id=0"
Signed-off-by: Július Milan <jmilan.dev@gmail.com> Reviewed-by: Jakub Grajciar <jgrajcia@cisco.com>