By Svea Herbst-Bayliss BOSTON (Reuters) – Jana Partners has nominated four directors to the board of Zendesk, arguing the company must be rehabilitated after an unpopular attempt to buy Momentive Global, parent of web-survey company SurveyMonkey, according to a letter seen by Reuters. Jana Partners launched the proxy contest a week before Zendesk shareholders are scheduled to vote on the company’s proposed acquisition of Momentive Global on Feb. 25. It also comes only a few days after Zendesk said it had rebuffed an approximately $17 billion bid from a consortium of private equity firms lookin…