net: Add vnet_hdr_len arguments in NetClientState

Add vnet_hdr_len arguments in NetClientState
that make other module get real vnet_hdr_len easily.

Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
diff --git a/net/net.c b/net/net.c
index 6235aab..b62ce10 100644
--- a/net/net.c
+++ b/net/net.c
@@ -492,6 +492,7 @@
         return;
     }
 
+    nc->vnet_hdr_len = len;
     nc->info->set_vnet_hdr_len(nc, len);
 }