sgsn: fix TC_iu_attach failing for recent -master

Since recently, osmo-sgsn is requesting encryption (UEA1 + UEA2)
in RANAP Security Mode Command by default [1].  The testcase
TC_iu_attach is assuming no encryption (UEA0) and thus failing.

Fix this by explicitly setting UEA0 via the VTY, similarly to
what testcase TC_iu_attach_encr does.

Change-Id: Ibaf83db1ab0f82f7e934e89ae3f6c19d014be197
Related: [1] osmo-sgsn.git I4eb9451b4267fc1436ed90a55ff200cf36f16bf6
diff --git a/sgsn/SGSN_Tests_Iu.ttcn b/sgsn/SGSN_Tests_Iu.ttcn
index 53aa032..f6a4243 100644
--- a/sgsn/SGSN_Tests_Iu.ttcn
+++ b/sgsn/SGSN_Tests_Iu.ttcn
@@ -35,6 +35,7 @@
 	var BSSGP_ConnHdlr vc_conn;
 	f_init();
 	f_sleep(1.0);
+	f_vty_config(SGSNVTY, "sgsn", "encryption uea 0");
 	vc_conn := f_start_handler(refers(f_TC_iu_attach), testcasename(), g_gb, 1001);
 	vc_conn.done;
 	f_cleanup();