Show progress dialog when uninstalling an app in Launcher3Go.

This ensures that the uninstall activity will finish only after
the task is completed.

We initially assumed that this was always the case, but in Android
Go the uninstall activity finishes before the uninstall is completed.

Bug: 64033585
Change-Id: Ic5d8dd99e2fecd0c9cb24093ee66668b4b38cb1a