Fix minimise all applet on wayland with an active window

Summary:
There's an async round trip after requesting isMinimized to kwin and
then back to Plasma with the updated roles.

There's a quirk on wayland that IsActive will update before we get
isMinimized changed. The old code would see that a window is currently
not minimised and deactivate the effect.

This patch checks the roles to only check after IsMinimized changes.

Test Plan: More clicking

Reviewers: Plasma, broulik

Reviewed By: Plasma, broulik

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D11133