net/virtio: improve vhost-user error logging
net/virtio: improve vhost-user error logging

This patch improves error logging in vhost_user_read,
especially printing errno when recv() fails.

Suggested-by: Adrian Moreno <4e5c605993413892a1c21f38afc464bef7695397@redhat.com>
Signed-off-by: Maxime Coquelin <9a2667dee3b90866bbc9c2696cff2b7d5616c95a@redhat.com>
Reviewed-by: Chenbo Xia <5d298a4585cd22ca5d29de25967a5599c4c324c8@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk