[Device Notifier] Fix transition animation
In the specific case of having the device notifier opened
and inserting a device that has been configured to be
automatically mounted, the transition animation could be
interrupted resulting in the opacity being wrong.
In the setup discribed in the summary, you should never
see something like the attached screenshot where the list
of action opacity is not 1.
for more information.
Subscribers: broulik, davidedmundson, ngraham, plasma-devel
Differential Revision: https://phabricator.kde.org/D17394