Summary:
Popup asking whether touchpad should be disabled stays open and can be covered by others, for example volume slider.
It is inconsistent since other elements of tray close themselves after switching away.

Depends on: D24825

BUG: 401016

Test Plan:
1. Disconnect all mouses
2. Click the touchpad icon
3. Try to dismiss it like every other tray plasmoid, for example by clicking on some other window.
4. Popup should consider itself dismissed

Reviewers: #plasma_workspaces, #plasma, davidedmundson

Reviewed By: #plasma_workspaces, #plasma, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D25158