fix unused variables

lib/app.php

lib/db.php

lib/filestorage.php

lib/filesystem.php

lib/filesystemview.php

lib/helper.php

lib/image.php

lib/migrate.php

lib/ocs.php

lib/ocsclient.php

lib/preferences.php

lib/setup.php

lib/streamwrappers.php

lib/template.php

lib/templatelayout.php

lib/util.php