Ryan Adams is famously: prolific, eccentric, smart, currently-sober, a very hip New Yorker, unpredictable and a little nuts. That said, nobody knows what they’re going to get when attending a Ryan Adams concert. Last night at DAR Constitution Hall, the alt-country musician gave the audience musical perfection and a heaping helping of tension. Ryan Adams and his band, The Cardinals, unassumingly took the stage to a half-empty room about an hour after the show…