When comic and “Curb Your Enthusiasm” director David Steinberg wanted a new title for an upcoming documentary on his career, he tested names at a recent birthday bash for Billy Crystal at Spago, where guests included friends and comedy icons Eric Idle, Paul Reiser and Richard Lewis. The new moniker? “Quality Balls,” which Steinberg told us comes from a Jerry Seinfeld quote on his current Showtime series, “Inside Comedy.” (Steinberg’s act infamously helped get the controversial 1960s “Smothers Brothers Comedy Hour” kicked off the air for rankling CBS censors, and Seinfeld described him as having “quality balls.”) The doc by Barry Avrich follows Steinberg from his record number of appearances on Johnny Carson’s “Tonight Show” to his recent La Jolla Playhouse gigs, and will debut at the prestigious Hot Docs festival. (We hear the working title for the film was “Prepare for the Worst,” a riff on Steinberg’s state of mind before going onstage, but perhaps not the most enticing name for expectant audiences.) “Inside Comedy,” exec produced by Steve Carell, this week featured Will Ferrell and Betty White.