net/9p: Use virtio transpart as the default transport

Make the default 9p experience better by defaulting to virtio transport if present.
These days most of the users are using 9p in a virtualized setup

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

net/9p/client.c

@@ -1014,6 +1014,9 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
 	if (err < 0)
 		goto destroy_tagpool;
 
+	if (!clnt->trans_mod)
+		clnt->trans_mod = v9fs_get_trans_by_name("virtio");
+
 	if (!clnt->trans_mod)
 		clnt->trans_mod = v9fs_get_default_trans();