mgw: new test TC_two_crcx_mdcx_and_rtp_clearmode

Add a test that uses SDP CLEARMODE towards the MGW. The SDP parameters
generated by the test look as expected when compared to RFC 4040
section 5.

Related: OS#4395
Related: https://www.rfc-editor.org/rfc/rfc4040#section-5
Change-Id: I89c5dfdcd728ab3b50e77c5062f07e1b802b1f01
diff --git a/mgw/MGCP_Test.ttcn b/mgw/MGCP_Test.ttcn
index 1a21974..6f25b20 100644
--- a/mgw/MGCP_Test.ttcn
+++ b/mgw/MGCP_Test.ttcn
@@ -2108,6 +2108,13 @@
 					   mp_local_ipv6, mp_remote_ipv6);
 	}
 
+	testcase TC_two_crcx_mdcx_and_rtp_clearmode() runs on dummy_CT {
+		f_tc_two_crcx_mdcx_and_rtp(mp_local_ipv4, mp_remote_ipv4,
+					   mp_local_ipv4, mp_remote_ipv4,
+					   120, /* 3GPP TS 48.103 table 5.4.2.2.1 */
+					   "CLEARMODE/8000");
+	}
+
 	/* Test what happens when two RTP streams from different sources target
 	 * a single connection. Is the unsolicited stream properly ignored? */
 	testcase TC_two_crcx_and_unsolicited_rtp() runs on dummy_CT {
@@ -2992,6 +2999,8 @@
 		execute(TC_two_crcx_mdcx_and_iuup_rtp());
 		execute(TC_two_crcx_mdcx_and_iuup_rtp_rfci_unordered());
 
+		execute(TC_two_crcx_mdcx_and_rtp_clearmode());
+
 		/* Note: This testcase will trigger an OSMO_ASSERT() bug in
 		 * older versions of osmo-mgw. This eventually leads into
 		 * a failure of all subsequent testcases, so it is important