Restore system tray SNI manual test
Summary:
In the change to the new system tray one of the old manual tests to run
SNIs got lost. This restores the version that was in Plasma 5.5.
Test Plan: Ran test. SNI appeared
Reviewers: Plasma, mart
Reviewed By: mart
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D3421