nat: Send a transcoder reset on start up.

The transcoder RESET is using the same extensions to reset all
endpoints on a remote site. This makes sure that all allocations
can be made in a properly configured network.
diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 7659527..b84a262 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -663,6 +663,15 @@
 		return -1;
 	}
 
+	if (mgcp_reset_transcoder(cfg) < 0) {
+		LOGP(DMGCP, LOGL_ERROR, "Failed to send packet to the transcoder.\n");
+		talloc_free(nat->bsc_endpoints);
+		nat->bsc_endpoints = NULL;
+		close(cfg->gw_fd.bfd.fd);
+		cfg->gw_fd.bfd.fd = -1;
+		return -1;
+	}
+
 	return 0;
 }