protocol: reject DLCX/CRCX/MDCX on unsupported parameters

When an unsupported MGCP parameter (e.g. N) is used, then this
parameter is ignored and the command execution continues. However,
an MGCP command that contains an unsupported parameter should
be rejected.

- Make sure that MGCP commands DLCX, CRCX and MDCX are rejected,
  when they contain unsupported parameters.

Change-Id: I8cd5987fc6befcd53a7c4916f77b1a24c904ba48
diff --git a/src/libosmo-mgcp/mgcp_protocol.c b/src/libosmo-mgcp/mgcp_protocol.c
index b0d9943..2cbd87b 100644
--- a/src/libosmo-mgcp/mgcp_protocol.c
+++ b/src/libosmo-mgcp/mgcp_protocol.c
@@ -535,6 +535,7 @@
 			LOGP(DLMGCP, LOGL_NOTICE,
 			     "CRCX: endpoint:%x unhandled option: '%c'/%d\n",
 			     ENDPOINT_NUMBER(endp), *line, *line);
+			return create_err_response(NULL, 539, "CRCX", p->trans);
 			break;
 		}
 	}
@@ -768,6 +769,7 @@
 			LOGP(DLMGCP, LOGL_NOTICE,
 			     "MDCX: endpoint:0x%x Unhandled MGCP option: '%c'/%d\n",
 			     ENDPOINT_NUMBER(endp), line[0], line[0]);
+			return create_err_response(NULL, 539, "MDCX", p->trans);
 			break;
 		}
 	}
@@ -918,6 +920,7 @@
 			LOGP(DLMGCP, LOGL_NOTICE,
 			     "DLCX: endpoint:0x%x Unhandled MGCP option: '%c'/%d\n",
 			     ENDPOINT_NUMBER(endp), line[0], line[0]);
+			return create_err_response(NULL, 539, "DLCX", p->trans);
 			break;
 		}
 	}