Improve search results when only phonebook-matches can we autocompleted

lib/composer/composer/autoload_classmap.php

lib/composer/composer/autoload_static.php

lib/private/Collaboration/Collaborators/UserPlugin.php

lib/private/User/Database.php

lib/private/User/Manager.php

lib/public/IUserManager.php

lib/public/User/Backend/IGetRealUIDBackend.php

lib/public/User/Backend/ISearchKnownUsersBackend.php

tests/lib/Collaboration/Collaborators/UserPluginTest.php