MGCP_Test: ts_CRCX_no_lco: check media description instead of media attribute

The testcase ts_CRCX_no_lco looks at the media attributes to see
if it findes the expected default codec there. In this testcase
we expect PCMU/8000/1 as media attribute, but this is a codec from
the fixed payload type domain. The MGW may not list this info inside
the media attributes. Listing the payload type number in the media
description is sufficient. We should check this instead.

- Remove media attribute check
- Check meida description for PCMU (0)

Change-Id: I69600a1025e68011e8fc5d8bf22d842d9c63bf53
Related: OS#2658

mgw/MGCP_Test.ttcn

@@ -326,7 +326,7 @@ module MGCP_Test {
 		/* See also OS#2658: Even when we omit the LCO information, we
 		   expect the MGW to pick a sane payload type for us. This
 		   payload type should be visible in the SDP of the response. */
-		if (resp.sdp.media_list[0].attributes[0].rtpmap.attr_value != "0 PCMU/8000/1") {
+		if (resp.sdp.media_list[0].media_field.fmts[0] != "0") {
 			setverdict(fail, "SDP contains unexpected codec");
 		}