sgsnemu: Convert from tun_setaddr() to tun_addaddr()

This converts the last caller of tun_setaddr() outside of lib/tun.c to
use tun_addaddr().

Change-Id: Ia301d6a4ee3d02c1af1c85f2fe1041d3013268b0
diff --git a/sgsnemu/sgsnemu.c b/sgsnemu/sgsnemu.c
index 8903d81..92abc70 100644
--- a/sgsnemu/sgsnemu.c
+++ b/sgsnemu/sgsnemu.c
@@ -1432,8 +1432,7 @@
 		if (addr.len == 16)
 			prefixlen = 64;
 		/* printf("Setting up interface and routing\n"); */
-		/* FIXME: use tun_addattr() not tun_setaddr() */
-		tun_setaddr(tun, &addr, &addr, prefixlen);
+		tun_addaddr(tun, &addr, &addr, prefixlen);
 		if (options.defaultroute) {
 			struct in_addr rm;
 			rm.s_addr = 0;