Make progress bar determinate when at 100%

This gives the user a better indication that the firmware update is done. The progress bar is still sorta disfunctional, but hey even disabled people are people.

Contributes to issue CURA-440.

plugins/USBPrinting/FirmwareUpdateWindow.qml

@@ -58,7 +58,7 @@ UM.Dialog
             value: manager.progress
             minimumValue: 0
             maximumValue: 100
-            indeterminate: true
+            indeterminate: manager.progress < 100
             anchors
             {
                 left: parent.left;