Bug#181081: cdebconf/text: Progress info overwrites itself

[Petter Reinholdtsen <pere@hungry.com>]

Package: cdebconf
Version: 0.30
Severity: minor

When anna uses the new progress feature, the progress text overwrites
the previous text without clearing the line.  This leads to rather
strange lines, like final line in my test install:

  [100.0%] Installing skolelinux-reportbug-udebb86udeb

I believe the line must be blanked before writing a new line, or
perhaps use trailing space at the end of the new line to overwrite the
previous text.