Revert commit d1843ebee1232df344badb42bb6e006aa328ecb4 that was supposed to improve the appearance of the StatusbarProgressWidget.

While appearance was improved a regression was introduced between the
time I tuned the appearance tweaks and the commit, with the result that
the statusbar was adjusted in height each time the widget appeared and
disappeared.
Reverting to remove that nuisance while I try to find a fix.