Fix multiple copy handling while printing

Both the printer code and the webengine printing code were
producing the number of requested copies. So if n copies were
requested, n*n copies of the document were printed.

Task-number: QTBUG-56722
Change-Id: I34bce2d61041e1234139139dcd70b7b3d1c7cd7b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>