bsc: Add testscase & infra to validate Osmux support BTS<->BSC

New TC_assignment_osmux_bts is added which tests Osmux used only
BTS<->BSC.
Existing TC_assignment_osmux is renamed to TC_assignment_osmux_cn,
and a new TC_assignment_osmux is added which tests using Osmux on both
sides (towards BTS and CN).

Related: SYS#5987
Change-Id: I6e82eb9d995de988b812001e1c4cf6923509de66
diff --git a/bsc/BSC_Tests_VAMOS.ttcn b/bsc/BSC_Tests_VAMOS.ttcn
index 131c2d4..cd9ffd0 100644
--- a/bsc/BSC_Tests_VAMOS.ttcn
+++ b/bsc/BSC_Tests_VAMOS.ttcn
@@ -299,7 +299,7 @@
 
 private function f_est_lchan_and_mode_modify_to_vamos() runs on MSC_ConnHdlr {
 	var PDU_BSSAP ass_cmd := f_gen_ass_req(g_pars.use_osmux_cn);
-	var template PDU_BSSAP exp_compl := f_gen_exp_compl(g_pars.use_osmux_cn);
+	var template PDU_BSSAP exp_compl := f_gen_exp_compl();
 
 	/* puzzle together the ASSIGNMENT REQ for given codec[s] */
 	if (mp_bssap_cfg[0].transport == BSSAP_TRANSPORT_AoIP) {