xbps-*: use xbps_pkgdb_update() correctly.

xbps-{alternatives,pkgdb,reconfigure}: xbps_pkgdb_update()
has been fixed to flush when told so, and we don't need
to update the in-memory copy because we are exiting.

bin/xbps-pkgdb/main.c

@@ -189,7 +189,7 @@ main(int argc, char **argv)
 
 out:
 	if (rv == 0)
-		xbps_pkgdb_update(&xh, true, true);
+		xbps_pkgdb_update(&xh, true, false);
 
 	xbps_end(&xh);
 	exit(rv ? EXIT_FAILURE : EXIT_SUCCESS);