fix various talloc / dynamic bts/trx related bugs

Prior to this patch, nanobts was not able to operate after recent changes
diff --git a/openbsc/src/telnet_interface.c b/openbsc/src/telnet_interface.c
index 8b9fd79..5cc6ea0 100644
--- a/openbsc/src/telnet_interface.c
+++ b/openbsc/src/telnet_interface.c
@@ -132,7 +132,7 @@
 	close(fd->fd);
 	bsc_unregister_fd(fd);
 	llist_del(&conn->entry);
-	free(conn);
+	talloc_free(conn);
 	return 0;
 }