Unmounting busy device doesn't tell who is blocking
Summary: Unmounting a busy device from the places panel doesn't tell which applications have open files blocking the unmount.
Test Plan:
Mount a USB stick using Dolphin
Open a file from the USB stick
Unmount the USB stick using Dolphin
Observe the new error message.
FEATURE: 189302
Reviewers: Dolphin, elvisangelaccio, ngraham, broulik, meven
Reviewed By: Dolphin, elvisangelaccio, meven
Subscribers: meven, davidedmundson, kfm-devel
Tags: Dolphin
Differential Revision: https://phabricator.kde.org/D19989