mgcp: Allow to omit sending the audio name at all

Equipment like AudioCode appears to get upset when we use a
builtin type and then assign a name to it. Allow to completely
omit the name.
diff --git a/openbsc/tests/vty_test_runner.py b/openbsc/tests/vty_test_runner.py
index 468d415..40053e3 100644
--- a/openbsc/tests/vty_test_runner.py
+++ b/openbsc/tests/vty_test_runner.py
@@ -77,6 +77,21 @@
 	self.assertEquals(res.find('  rtp force-ptime 20\r'), -1)
 	self.assertEquals(res.find('  no rtp force-ptime\r'), -1)
 
+    def testOmitAudio(self):
+        self.vty.enable()
+	res = self.vty.command("show running-config")
+	self.assert_(res.find('  sdp audio-payload send-name\r') > 0)
+	self.assertEquals(res.find('  no sdp audio-payload send-name\r'), -1)
+
+	self.vty.command("configure terminal")
+	self.vty.command("mgcp")
+	self.vty.command("no sdp audio-payload send-name")
+	res = self.vty.command("show running-config")
+	self.assertEquals(res.find('  rtp sdp audio-payload send-name\r'), -1)
+	self.assert_(res.find('  no sdp audio-payload send-name\r') > 0)
+
+        # TODO: test it for the trunk!
+
 
 class TestVTYGenericBSC(TestVTYBase):