D20433: Use mount point returned from DBus instead of using property value

[Kai Uwe Broulik]

broulik added a reviewer: bruns.

REPOSITORY
  R245 Solid

REVISION DETAIL
  https://phabricator.kde.org/D20433

To: nicolasfella, broulik, bruns
Cc: kde-frameworks-devel, michaelh, ngraham, bruns