The Tesla CEO made it even harder for rivals to sell their electric cars — With his aw-shucks, confessional, good-sport, loves-his-mom, boyishly eager-to-please star turn on Saturday Night Live, Tesla’s Elon Musk did what the CEOs of Volkswagen, Ford, GM and everyone else in the electric vehicle race know they cannot: yuk it up as an equal alongside pop culture celebrities, and then hog the…