bsc: Submit valid l3 payload

OsmoBSC does some minimal parsing of l3 content to select MSC target,
match paging response to paging request, etc.
Since tests right now use potentially invalid data, osmo-bsc is not
rejecting conns providing invalid l3 content.

This commit makes sure TTCN3 tests pass valid l3 payloads to osmo-bsc,
so that they keep working once osmo-bsc starts rejecting invalid IEs it
parses.

Related: SYS#6280
Change-Id: I6e99ac39f32c9a981420b73f8d7d1568d2fa1c54
diff --git a/bsc/BSC_Tests_VAMOS.ttcn b/bsc/BSC_Tests_VAMOS.ttcn
index 3ebcaaa..1dc4910 100644
--- a/bsc/BSC_Tests_VAMOS.ttcn
+++ b/bsc/BSC_Tests_VAMOS.ttcn
@@ -280,12 +280,12 @@
 private function f_verify_dtap() runs on MSC_ConnHdlr
 {
 	var PDU_BSSAP rx_bssap_dtap;
-	var octetstring l3_data;
+	var octetstring l3_data := gen_l3_valid_payload();
 
 	/* MS to NW */
-	RSL.send(ts_RSL_DATA_IND(g_chan_nr, valueof(ts_RslLinkID_DCCH(0)), c_l3_payload));
+	RSL.send(ts_RSL_DATA_IND(g_chan_nr, valueof(ts_RslLinkID_DCCH(0)), l3_data));
 	BSSAP.receive(tr_BSSAP_DTAP) -> value rx_bssap_dtap;
-	if (not match(rx_bssap_dtap.pdu.dtap, c_l3_payload)) {
+	if (not match(rx_bssap_dtap.pdu.dtap, l3_data)) {
 		setverdict(fail, "unexpected L3 data");
 		mtc.stop;
 	}