bsc: Fix tons of TTCN3 compiler warnings

Change-Id: I60dc054d19a249d46d44585c17626746c34f4b09
diff --git a/library/Osmocom_VTY_Functions.ttcn b/library/Osmocom_VTY_Functions.ttcn
index ccea0f2..9258fa5 100644
--- a/library/Osmocom_VTY_Functions.ttcn
+++ b/library/Osmocom_VTY_Functions.ttcn
@@ -74,7 +74,7 @@
 
 	/* send a VTY command and obtain response until prompt is received */
 	function f_vty_transceive(TELNETasp_PT pt, charstring tx) {
-		f_vty_transceive_ret(pt, tx);
+		var charstring unused := f_vty_transceive_ret(pt, tx);
 	}
 
 	type integer BtsNr (0..255);