"I was a bartender, a hot-dog vendor, a cook, sold magazine subscriptions," recounted a sleepy-voiced John Rzeznik during a recent telephone interview, "and if I wasn't doing this, I'd probably be finishing my degree in sociology."Rzeznik was not tired because of any day job, but from late nights put in as front man for The Goo Goo Dolls. The Buffalo, N.Y., trio, which will perform tonight at Starz nightclub in Allentown, is in the midst of a tour in support of "A Boy Named Goo" (Metal Blade/Warner Bros.), its latest disc. "A Boy Named Goo," the nine-year-old group's fif