Make code strict

apps/dav/lib/CardDAV/Converter.php

apps/dav/tests/unit/CardDAV/ConverterTest.php

apps/dav/tests/unit/CardDAV/SyncServiceTest.php

apps/provisioning_api/lib/Controller/AUserData.php

apps/provisioning_api/lib/Controller/UsersController.php

...rovisioning_api/tests/Controller/GroupsControllerTest.php

...provisioning_api/tests/Controller/UsersControllerTest.php

apps/settings/lib/BackgroundJobs/VerifyUserData.php

apps/settings/lib/Controller/UsersController.php

apps/settings/lib/Settings/Personal/PersonalInfo.php

apps/settings/tests/Controller/UsersControllerTest.php

lib/private/Accounts/AccountManager.php

lib/private/Accounts/Hooks.php

tests/lib/Accounts/HooksTest.php