virtio-net: revert mac on reset

Once guest overrides virtio net primary mac,
it retains the value set until qemu exit.
This is inconsistent with standard nic behaviour.
To fix, revert the mac to the original value on reset.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/virtio-net.c

@@ -199,6 +199,7 @@ static void virtio_net_reset(VirtIODevice *vdev)
     n->mac_table.multi_overflow = 0;
     n->mac_table.uni_overflow = 0;
     memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
+    memcpy(&n->mac[0], &n->nic->conf->macaddr, sizeof(n->mac));
     memset(n->vlans, 0, MAX_VLAN >> 3);
 }