[System Tray Containment] Ungrab mouse before opening context menu

Authored by broulik on Feb 6 2017, 12:37 PM.

Description

[System Tray Containment] Ungrab mouse before opening context menu

This is the same Plasma ContainmentInterface does. Otherwise QtQuick gets confused about mouse state.

Differential Revision: https://phabricator.kde.org/D4455