The private log(Exception) method built an IStatus and discarded it, never
actually logging anything. It has been broken since it was introduced in
2004. The only caller swallows InvocationTargetException and
InterruptedException from ProgressMonitorDialog.run(); inline that swallow
with a comment explaining why the interrupt flag is not re-set
(ModalContext.run uses InterruptedException to signal cancellation, not
actual thread interruption).

Fixes https://github.com/eclipse-platform/eclipse.platform.ui/issues/3915