D18904: [FileCopyJob] Clean up after file copy operation is cancelled

[Chinmoy Ranjan Pradhan]

chinmoyr added a dependency: D19080: [WIP] Make file overwrite a bit safer.

REPOSITORY
  R241 KIO

REVISION DETAIL
  https://phabricator.kde.org/D18904

To: chinmoyr, dfaure, dmitrio
Cc: kde-frameworks-devel, ngraham, michaelh, bruns