MaintenanceTool crash during updates

It seems that the root cause might be the QDebug usage in a multithread environment.

The main thread uses qDebug() in ProgressCoordinator::partProgressChanged() and runOperation() also uses qDebug() (through OperationTracer class) in a thread (started by PackageManagerCorePrivate::runPackageUpdater() -> PackageManagerCorePrivate::runUndoOperations() -> PackageManagerCorePrivate::performOperationThreaded()).

this will eventually lead to qBadAlloc on QDebug::~QDebug(). I cannot attach the dumb file as it is too big in size