bsc: fix TC_ho_into_this_bsc_a5_4

This test should be failing as it is, because A5/4 is not permitted in
the BSC's configuration! It only passed all this time because osmo-bsc
is/was/is going to have been flawed and just takes the Chosen Encryption
Algorithm IE as the basis for choosing an encryption algorithm. Instead
it should intersect the pemitted algos with the BSC config. It will soon
do that, and then this test would fail as it should have. After fixing
the BSC config for the test with this patch, we'll not see it failing in
the transition.

Related: SYS#5839
Change-Id: Ic6bbbeea36e6ea26d16bbb510fd08f5c0defb955
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index 5b7243b..45c3239 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -3743,9 +3743,11 @@
 	f_vty_transceive(BSCVTY, "exit");
 }
 
+const charstring VTY_A5_DEFAULT := "0 1 3";
+
 private function f_vty_encryption_a5_reset() runs on test_CT {
 	/* keep in sync with docker-playground.git ttcn3-bsc-test/osmo-bsc.cfg */
-	f_vty_encryption_a5("0 1 3");
+	f_vty_encryption_a5(VTY_A5_DEFAULT);
 }
 
 /* Establish signalling channel (non-assignment case) followed by cipher mode */
@@ -6087,12 +6089,13 @@
 	f_perform_clear(exp_rr_rel_tmpl := exp_rr_rel_tmpl);
 	setverdict(pass);
 }
-function f_tc_ho_into_this_bsc_main(TestHdlrParams pars) runs on test_CT {
+function f_tc_ho_into_this_bsc_main(TestHdlrParams pars, charstring vty_a5_cfg := VTY_A5_DEFAULT) runs on test_CT {
 	var MSC_ConnHdlr vc_conn;
 
 	f_init(1, true);
 	f_sleep(1.0);
 
+	f_vty_encryption_a5(vty_a5_cfg);
 	f_ctrs_bsc_and_bts_handover_init();
 
 	pars.sccp_addr_msc := g_bssap[0].sccp_addr_own;
@@ -6106,6 +6109,8 @@
 	f_ctrs_bsc_and_bts_add(0, "interbsc_ho_in:attempted");
 	f_ctrs_bsc_and_bts_add(0, "interbsc_ho_in:completed");
 	f_ctrs_bsc_and_bts_verify();
+
+	f_vty_encryption_a5_reset();
 }
 
 testcase TC_ho_into_this_bsc() runs on test_CT {
@@ -6114,10 +6119,10 @@
 	f_shutdown_helper();
 }
 
-function f_tc_ho_into_this_bsc_a5(TestHdlrEncrParams encr) runs on test_CT {
+function f_tc_ho_into_this_bsc_a5(TestHdlrEncrParams encr, charstring vty_a5_cfg := VTY_A5_DEFAULT) runs on test_CT {
 	var TestHdlrParams pars := f_gen_test_hdlr_pars();
 	pars.encr := encr;
-	f_tc_ho_into_this_bsc_main(pars);
+	f_tc_ho_into_this_bsc_main(pars, vty_a5_cfg);
 	f_shutdown_helper();
 }
 
@@ -6134,7 +6139,7 @@
 }
 
 testcase TC_ho_into_this_bsc_a5_4() runs on test_CT {
-	f_tc_ho_into_this_bsc_a5(f_encr_params('10'O, kc128 := true));
+	f_tc_ho_into_this_bsc_a5(f_encr_params('10'O, kc128 := true), "3 4");
 }
 
 /* Report: in inter-BSC incoming handover, when the MSC omits the Chosen Encryption Algorithm IE in the Handover Request