If the host of a kjob crashes or is killed kuiserver currently reports
that the job has been completed successfully. This is seriously wrong as
it could lead a user to perform a potentially destructive operation.
Setting any error (that's not 0 or 1) will cause plasmashell, the main
kuiserver view, to show a persistent notification that a job has failed.
For master I will use a more correct new enum, new error text, and a way
to tell for KIO operations to report to the uiserver if the host
crashing is important or not.