Plenty of rock stars wear tattoos, but a few tattoos equal the creamy pastel vision on Johnny Rzeznik's right biceps. It's a copy of Picasso's "The Dream," a modernist Mona Lisa lounging on a red chair, and Rzeznik (the first z is silent) readily shares his interpretation. "She has her eyes closed and this great look on her face," says the Goo Goo Dolls' singer and guitarist. "She has six fingers, and she's obviously masturbating while dreaming about Picasso."In a few hours, Rzeznik's band will play the Day in the Garden Festival, on the site of the original Woodstock, in upstate New York. Rig