Add a new paramter (flags) to rte_vhost_driver_register(). DPDK
vhost-user acts as client mode when RTE_VHOST_USER_CLIENT flag
is set. The flags would also allow future extensions without
breaking the API (again).
The rest is straingfoward then: allocate a unix socket, and
bind/listen for server, connect for client.
This extension is for vhost-user only, therefore we simply quit
and report error when any flags are given for vhost-cuse.
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
64ab701c3d