mgcp/test: Don't reset conn_mode between messages

Currently, the conn_mode field is reset after it has been checked.

This patch disables this behaviour and only adds a mark (bit) to
detect modifications.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/tests/mgcp/mgcp_test.c b/openbsc/tests/mgcp/mgcp_test.c
index 1f11b1d..fa68867 100644
--- a/openbsc/tests/mgcp/mgcp_test.c
+++ b/openbsc/tests/mgcp/mgcp_test.c
@@ -416,9 +416,7 @@
 			endp->net_end.packet_duration_ms = -1;
 			endp->local_options.pkt_period_min = 0;
 			endp->local_options.pkt_period_max = 0;
-			endp->conn_mode = MGCP_CONN_NONE | CONN_UNMODIFIED;
-			endp->net_end.output_enabled = 0;
-			endp->bts_end.output_enabled = 0;
+			endp->conn_mode |= CONN_UNMODIFIED;
 		}