zebra: Lookup up nlsock * one time in call tree

Code is looking up the nlsock to generate the batch messages
and then looking it up again to get the response.  Let's
just look it up one time.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

zebra/kernel_netlink.c

@@ -1289,18 +1289,15 @@ int netlink_request(struct nlsock *nl, void *req)
 	return 0;
 }
 
-static int nl_batch_read_resp(struct nl_batch *bth)
+static int nl_batch_read_resp(struct nl_batch *bth, struct nlsock *nl)
 {
 	struct nlmsghdr *h;
 	struct sockaddr_nl snl;
 	struct msghdr msg = {};
 	int status, seq;
-	struct nlsock *nl;
 	struct zebra_dplane_ctx *ctx;
 	bool ignore_msg;
 
-	nl = kernel_netlink_nlsock_lookup(bth->zns->sock);
-
 	msg.msg_name = (void *)&snl;
 	msg.msg_namelen = sizeof(snl);
 
@@ -1493,7 +1490,7 @@ static void nl_batch_send(struct nl_batch *bth)
 			err = true;
 
 		if (!err) {
-			if (nl_batch_read_resp(bth) == -1)
+			if (nl_batch_read_resp(bth, nl) == -1)
 				err = true;
 		}
 	}