openswan: Fix nat traversal not working

before using udp encap, need call udp_encap_enable
otherwise, the udp encap packets will go to the socket creator.

Change-Id: I267179c71c646a8d11984990cabe99e198e32322
Signed-off-by: Ken Zhu <guigenz@codeaurora.org>

openswan/patches/230-call-udp_encap_enable.patch

+diff -Nur a/linux/net/ipsec/ipsec_tunnel.c openswan-2.6.41/linux/net/ipsec/ipsec_tunnel.c
+--- a/linux/net/ipsec/ipsec_tunnel.c	2019-04-03 16:15:42.236848820 -0700
++++ openswan-2.6.41/linux/net/ipsec/ipsec_tunnel.c	2019-04-03 16:17:57.724844808 -0700
+@@ -1731,6 +1731,9 @@
+ 	sk->sk_destruct        = ipsec_tunnel_udp_encap_destruct;
+ 	udp_sk(sk)->encap_type = encap_type;
+ 	udp_sk(sk)->encap_rcv  = klips26_udp_encap_rcv;
++#ifdef NEED_UDP_ENCAP_ENABLE
++	udp_encap_enable();
++#endif
+ 
+ 	/* add the tunnel to our list so we can check on it later */
+ 	list_add(&ctx->link, &ipsec_tunnel_udp_encap_list);