BTS_Tests: f_rtpem_activate(): make RTP payload type configurable

Change-Id: I84f576f578ffc48c8b5e545bc1700000eb693efb
Related: OS#1572
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 1b43797..cd13688 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -2609,7 +2609,8 @@
 /* Initialize and start the RTP emulation component for a ConnHdlr */
 friend function f_rtpem_activate(inout octetstring payload,
 				 RtpemConfig cfg := c_RtpemDefaultCfg,
-				 RtpemMode mode := RTPEM_MODE_BIDIR)
+				 RtpemMode mode := RTPEM_MODE_BIDIR,
+				 uint7_t rtp_pt := 0)
 runs on ConnHdlr {
 	/* Step 0: initialize, connect and start the emulation component */
 	vc_RTPEM := RTP_Emulation_CT.create(testcasename() & "-RTPEM");
@@ -2672,7 +2673,7 @@
 		ts_RSL_IPA_MDCX(g_chan_nr, conn_id,
 				remote_ip := f_inet_addr(mp_rtpem_bind_ip),
 				remote_port := rtpem_bind_port,
-				rtp_pt2 := 0),
+				rtp_pt2 := rtp_pt),
 		tr_RSL_IPA_MDCX_ACK(g_chan_nr, conn_id, ?, ?, ?),
 		"IPA MDCX ACK");