Make progress/progressbar work when uploading multiple files

[fohrloop]

This considers the flow-dev branch (599f6ff). When uploading files, the progressbar / progress jumps.

For example, when uploading two files with about the same size

• First, the progress goes from 0 to 55% (first file)
• Then, the progress goes from 0 to 100% (second file)

The progress is read from the flowComponent.progress().

What would be expected that during the second file, the progress goes from 55% to 100%.

[fohrloop]

Fixed in ffc44d2