Do not treat ENOENT and ENOTDIR differently in stat()

Summary: Any error returned from browse_stat_path() should probably be signaled as error to KIO. Previous behavior only showed a warning and continued as if the operation completed fine if browse_stat_path() returned either ENOENT or ENOTDIR.

Reviewers: elvisangelaccio

Reviewed By: elvisangelaccio

Differential Revision: https://phabricator.kde.org/D6664