backup: more feedback during restore
backup: more feedback during restore

The upload of a backup can take a while, so pop up the work dialog as
soon as that starts, not only when it is finished.

Jaesin/OctoPrint,foosel/OctoPrint,foosel/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint,Jaesin/OctoPrint