Rainn Wilson, from left, Aasif Mandvi and Adam Stein in “Waiting for Godot” at Geffen Playhouse in Los Angeles. What’s most surprising about the excellent Geffen Playhouse production of Samuel Beckett’s “Waiting for Godot,” starring Rainn Wilson, is how subdued the clowning is from two actors known for their offbeat comic talents. Rainn Wilson, from left, Conor Lovett and Adam …