It sounds like quite an unlikely collaboration –  rock legend Lou Reed making a record backed the massively successful heavy metal group Metallica. Their new concept album, “Lulu,” is out today in North America, and has left some music fans a bit bemused.  A recent review in The Washington Post called it a “multi-headed hydra of unpleasantness.”  Ben Sisario, music journalist and reporter for  The New York Times,  met with “Loutallica”  recently, and has a more nuanced view of the new record.