util: support setting peer for virNetDevIPInfo addresses

This will apply to any IP address setting that uses
virNetDevIPInfoAddToDev() (which so far is only the guest-side of LXC
type='ethernet' interfaces).

src/util/virnetdevip.c

@@ -918,7 +918,7 @@ virNetDevIPInfoAddToDev(const char *ifname,
                            ipStr);
             goto cleanup;
         }
-        if (virNetDevIPAddrAdd(ifname, &ip->address, NULL, prefix) < 0)
+        if (virNetDevIPAddrAdd(ifname, &ip->address, &ip->peer, prefix) < 0)
             goto cleanup;
         VIR_FREE(ipStr);
     }