[QA] shows "saved" message, when the file cannot be saved

[jnweiger]

Seen with 2.311 on oc10.7.0

• Configure WND drive with samba.

• place an empty hello.txt file in the samba drive, as root user.

• run occ file:scan --all - the hello.txt file shows up in the web UI.

• edit wth files_texteditor, add some lines of text.

• Messages appear: "Saving..." - "saved"

• In fact the file was not saved. BAD. The file size in the storage is still 0, the permission are still root user only.

Expected behaviour: show proper error message, when a file cannot be overwritten