BTS_Tests.ttcn: add 'lazy' mode for as_meas_res()

This mode would be useful for test cases, which expect to receive
the RSL_MEAS_RES messages, but don't care about their correctness.

Change-Id: I39118d6e64c767fad2c9618ec0ef4532dc60e715
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index fe59fd3..9c749b4 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -1296,8 +1296,9 @@
 }
 
 /* verify we regularly receive measurement reports with incrementing numbers */
-altstep as_meas_res() runs on ConnHdlr {
+altstep as_meas_res(boolean verify_meas := true) runs on ConnHdlr {
 	var RSL_Message rsl;
+	[not verify_meas] RSL.receive(tr_RSL_MEAS_RES(?)) { repeat; }
 	[] RSL.receive(f_build_meas_res_tmpl()) -> value rsl {
 		/* increment counter of next to-be-expected meas rep */
 		g_next_meas_res_nr := (g_next_meas_res_nr + 1) mod 256;