respond to HNBAP UE REGISTER REQ withe correspnding ACCEPT

The Accept incudes the IMSI that the phone presented, but
somehow we fail to encode the Context ID as bitstring,  see
../pcap/20150911-hnbap-ue_register.pcap
diff --git a/src/hnbgw.c b/src/hnbgw.c
index ac0d03c..b50cd9d 100644
--- a/src/hnbgw.c
+++ b/src/hnbgw.c
@@ -9,6 +9,7 @@
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/sctp.h>
+//#include <arpa/inet.h>
 
 #include <osmocom/core/application.h>
 #include <osmocom/core/talloc.h>
@@ -245,6 +246,7 @@
 	g_hnb_gw.listen_fd.cb = listen_fd_cb;
 	g_hnb_gw.listen_fd.when = BSC_FD_READ;
 	g_hnb_gw.listen_fd.data = &g_hnb_gw;
+	g_hnb_gw.next_ue_ctx_id = 23;
 	INIT_LLIST_HEAD(&g_hnb_gw.hnb_list);
 	INIT_LLIST_HEAD(&g_hnb_gw.ue_list);