Make sure maintenance mode is always casted to bool

apps/dav/lib/Connector/Sabre/MaintenancePlugin.php

apps/encryption/lib/AppInfo/Application.php

core/Command/Encryption/DecryptAll.php

core/Command/Encryption/EncryptAll.php

core/Command/Maintenance/Mode.php

core/Command/Maintenance/Repair.php

core/Command/Upgrade.php

cron.php

lib/base.php

lib/private/Console/Application.php

lib/private/Route/Router.php

lib/private/Updater.php

lib/private/legacy/app.php

ocs/v1.php