ovn-northd: Don't shadow addr_family in add_router_lb_flow().

This is a partial backport of commit 396d492 ("Don't shadow
variables.") to fix a build break due to backporting a different commit
that depended on it.

Reported-by: Flavio Leitner <fbl@sysclose.org>
CC: Mark Michelson <mmichels@redhat.com>
Fixes: 15fbc3b ("ovn: Add router load balancer undnat rule for IPv6")
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Acked-by: Mark Michelson <mmichels@redhat.com>

ovn/northd/ovn-northd.c

@@ -4463,9 +4463,9 @@ add_router_lb_flow(struct hmap *lflows, struct ovn_datapath *od,
     while (ip_str && ip_str[0]) {
         char *ip_address = NULL;
         uint16_t port = 0;
-        int addr_family;
+        int addr_family_;
         ip_address_and_port_from_lb_key(ip_str, &ip_address, &port,
-                                        &addr_family);
+                                        &addr_family_);
         if (!ip_address) {
             break;
         }