The Metropolitan Opera season is over and summer festivals featuring opera (Bard, Caramoor, Mostly Mozart, not to mention Saratoga Springs and Tanglewood for long weekends) are months away, the New York Opera Fest takes place all over town through June 30.  The schedule features operas from its Baroque origins through the present.   On May 9-11 at the GK ArtsCenter , little opera theatre of NY (LOTNY) presented the NY premiere of Benjamin Britten's Owen Wingrave, written for television in 1971.  Yes, opera was part of pre-cable television, and Britten wasn't the hard sell the Met now treats his as. Based on a short short by