bsc: TC_stats_conn_fail: fix for sccplite

Change the test so OsmoBSC always sends an BSSAP Assignment Failure by
setting the Data Indicator to an invalid value. Previously the test had
assumed that OsmoBSC would always send an Assignment Failure when
requesting CSD as it was not yet implemented.

The test only passed by chance on AoIP: OsmoBSC rejects the CSD
Assignment Request unless it has the Speech Codec List IE for AoIP.

Related: OS#4393
Change-Id: Ia4e8ab01dbadae5c9d7a964c0760dd3b016ab606

bsc/BSC_Tests.ttcn

@@ -2095,8 +2095,9 @@ private function f_TC_stats_conn_fail(charstring id) runs on MSC_ConnHdlr {
 
 	f_statsd_reset();
 
-	/* Establish SDCCH */
+	/* Establish SDCCH (invalid DataIndicator for exp_fail) */
 	ass_cmd.pdu.bssmap.assignmentRequest.channelType := valueof(ts_BSSMAP_IE_ChannelTypeCSD);
+	ass_cmd.pdu.bssmap.assignmentRequest.channelType.speechId_DataIndicator := 'ff'O;
 	f_establish_fully(ass_cmd, exp_fail);
 
 	/* Expect stats to be 0 */