msc: add TC_lu_imsi_auth_tmsi_encr_3_1_log_msc_debug (OS#2947)

To trigger the segfault described in OS#2947, run TC_lu_imsi_auth_tmsi_encr_3_1
with logging category for MSC to set to debug.

Change-Id: I72a1dbb30e0a39dbf4b81c7e378d5607b62e10d3
diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index daadc2b..976cf0d 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -1484,6 +1484,19 @@
 	vc_conn := f_start_handler_with_pars(refers(f_tc_lu_imsi_auth_tmsi_encr_3_1), pars);
 	vc_conn.done;
 }
+testcase TC_lu_imsi_auth_tmsi_encr_3_1_log_msc_debug() runs on MTC_CT {
+	var BSC_ConnHdlr vc_conn;
+	f_init();
+	f_vty_config(MSCVTY, "network", "authentication required");
+	f_vty_config(MSCVTY, "network", "encryption a5 3");
+
+	/* Make sure the MSC category is on DEBUG level to trigger the log
+	 * message that is reported in OS#2947 to trigger the segfault */
+	f_vty_config(MSCVTY, "log stderr", "logging level msc debug");
+
+	vc_conn := f_start_handler(refers(f_tc_lu_imsi_auth_tmsi_encr_3_1), 362);
+	vc_conn.done;
+}
 
 /* A5/1 + A5/3 only permitted on network side, and MS with only A5/2 support */
 private function f_tc_lu_imsi_auth_tmsi_encr_13_2(charstring id, BSC_ConnHdlrPars pars) runs on BSC_ConnHdlr {
@@ -1646,6 +1659,8 @@
 
 	execute( TC_lu_and_mt_call() );
 
+	/* Run this last: at the time of writing this test crashes the MSC */
+	execute( TC_lu_imsi_auth_tmsi_encr_3_1_log_msc_debug() );
 }