MSC: add a test case to check T3212 expiration during paging

Long story short: some time ago I noticed that OsmoMSC crashes if
T3212 expires during the Paging procedure. This is not the case
anymore (as the test case shows) and apparently the bug has been
fixed, hovewer I believe it makes sense to add this test case.

Change-Id: If9147ae8b07d5120d2853b9acda2313910ac48be
diff --git a/msc/MSC_Tests_Iu.ttcn b/msc/MSC_Tests_Iu.ttcn
index 72bbf03..febae09 100644
--- a/msc/MSC_Tests_Iu.ttcn
+++ b/msc/MSC_Tests_Iu.ttcn
@@ -523,6 +523,14 @@
 	vc_conn.done;
 }
 
+testcase TC_iu_lu_and_expire_while_paging() runs on MTC_CT {
+	var BSC_ConnHdlr vc_conn;
+	f_init(3);
+	vc_conn := f_start_handler(refers(f_tc_lu_and_expire_while_paging), 1055,
+				   ran_idx := 2, ran_is_geran := false);
+	vc_conn.done;
+}
+
 control {
 	execute( TC_iu_lu_imsi_reject() );
 	execute( TC_iu_lu_imsi_timeout_gsup() );
@@ -582,6 +590,7 @@
 	execute( TC_iu_multi_lu_and_mt_ussd() );
 
 	execute( TC_iu_lu_with_invalid_mcc_mnc() );
+	execute( TC_iu_lu_and_expire_while_paging() );
 
 	/* TODO: Iu + SGsAP related tests, e.g. paging on IuCS */