By John Revill and Oliver Hirt ZURICH (Reuters) - Nestle investors are hoping the Swiss food group can draw a line under a period of volatility and sliding shares after the company accelerated the departure of its chairman, hot on the heels of a scandal that toppled its CEO. After the early exit of Chairman Paul Bulcke, 71, former Inditex CEO Pablo Isla will take the reins on October 1, half a year ahead of schedule, challenged to revive the fortunes of the maker of KitKat chocolate and Nescafe coffee by ...