MILAN (Reuters) -Italy's largest insurer Generali said on Monday it had fired veteran executive Luciano Cirina, who is publicly challenging incumbent Philippe Donnet for the role of chief executive, for alleged breach of contract. Cirina, who was head of Austria and the CEE countries at the insurer, has been proposed for the top job by a leading Generali investor in a power struggle which will be put to a shareholder vote on April 29.