Round 2 for this bug. Now we handle missing auth as an expected result
rather than a failure. FTP operations are now well tested and this patch
does not affect code shared with other components.
Side-effect is that browser authentication popups now appear when the
FTP server needs authentication. This has been a long missed event.
The root cause of the issue is not found so other subsequent errors in
FTP sub-protocol still silently lost due to the same issue.