NEW YORK, Aug 30(Reuters) – Shareholders in China's Hollysys Automation Technologies owning a total 32.2% of the automation control system maker's shares asked the board of directors to set a special shareholder meeting, according to a letter seen by Reuters. Asking for a special meeting is a highly unusual step and signals shareholders' mounting frustration with management of the U.S.-listed company, which has received takeover bids but which has not started a sales process, people familiar with the matter said. The letter was sent to the company on behalf of 33 investors, including hedge funds Oasis Management and Maso Capital,…