bsc: Use f_rnd_ra_emerg() instead of hardcoded value

Change-Id: Id10d71868dc8ef427e0353ee4b7e51d5bebc6255
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index c3743df..909b71f 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -10466,7 +10466,7 @@
 	/* Make sure the CHAN RQD indicates an emergency call (0b101xxxxx). The difference is that osmo-bsc directly
 	 * assigns a TCH lchan and establishing voice for the emergency call will use Mode Modify, not reassignment to
 	 * another lchan. */
-	g_pars.ra := 'b7'O;
+	g_pars.ra := f_rnd_ra_emerg();
 	f_assignment_emerg_setup();
 
 	var PDU_BSSAP emerg_setup_data_ind_bssap;