(Reuters) - Supervalu Inc struck a $3.3 billion deal to reduce its burdensome debt by selling five of its supermarket chains to an investor group led by Cerberus Capital Management LP , the No. 3 U.S. grocery store operator said on Thursday. Supervalu has been losing customers to rivals like Kroger Co and Wal-Mart Stores Inc . News of the pending asset sale sent its shares up more than 14 percent on the New York Stock Exchange. ...