KIO: add SlaveBase::openPasswordDialogV2 for better error checking.
Review Request #128289 - Created June 26, 2016 and submitted
Instead of bool return value, V2 provides an int (job error) return value. This allows to differenciate between "user canceled" and "error communicating with kpasswdserver". This is important because upon "user canceled" the job just finishes silently, so the user thinks the operation succeeded when in fact it got silently canceled, very dangerous. The actual communication error dated from when kpasswdserver was in kded rather than kiod (and on a computer with kded5 not installed), but still, let's make this robust to avoid a possible data loss situation.
- when cancelling, no error
- when uninstalling kiod5 and killing it, "Communication with local password server failed" error appears