univention-samba4-backup: don't touch backups every day

The backups get their permissions changed every time the script is running. This changes the ctime of the file and causes inclusion to systembackups (e.g. bareos). This is especially annoying when many backupfiles are kept or the files are large.

In f065824 calling "chmod" for every files was added, now we do it only for files with wrong permissions.

services/univention-samba4/sbin/univention-samba4-backup

@@ -97,5 +97,5 @@ install -o root -g root -m 700 -d "$WHERE"
 
 umask 0026 # samba-tool updates private/sam.ldb.d/metadata.tdb
 samba-tool domain backup offline --targetdir="$WHERE" || die "ERROR: samba-tool domain backup failed"
-chmod 600 "$WHERE"/samba-backup-*.bz2
+find "$WHERE" -name samba-backup-*.bz2 -a ! -perm 600 -print0 | xargs -0 chmod 600
 clean_old_backups 'samba/samba-backup-.*.bz2' "$DAYS"