There is no need to make the vhost user channel nonblock, and
making it nonblock will make vhost_user_read() fail with EAGAIN
when vhost messages need a reply.
Fixes: bd8f50a45d ("net/virtio-user: support server mode")
Cc: stable@dpdk.org
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>