There's a Janis Joplin tribute band playing in Phoenix, and as the late '60s icon herself would say, "Get it while you can."Phoenix resident Susan Ballard has been impersonating blues singer Janis Joplin since 1997, when she played her first tribute show at a club on 7th Avenue called Desert Rose. The show coming up on Sunday, February 22 is a homecoming of sorts -- it'll be at zGirl club, formerly known as Misty's, formerly known as Desert Rose. "It's going to be madness," Ballard says. "It's a