Some more Qt5 QT_VERSION fixes.

Change-Id: I1b3596939cd4aca2b91da3f5b09f50f2639b6fbd
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Niels Weber <niels.weber@digia.com>
Fix crash while canceling the meta data unzip task.

The crash happens cause in reset we do a delete later on the
unzip tasks and then a second delete while not checking early
enough for the set error code.

Change-Id: Iee17cd6863435d25c0c999fb0cc4e05672de3cc8
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Add important note.

Change-Id: Ifa7364d561b8fbb3370f8e3930e62c040280fe17
Reviewed-by: Niels Weber <niels.weber@digia.com>