By Rob Lenihan The billionaire gives up on a position that would have allowed him to influence Twitter’s future. Twitter (TWTR) – Get Twitter, Inc. Report went into high gear after Tesla (TSLA) – Get Tesla Inc Report CEO Elon Musk decided not to join the social media site’s board of directors. Musk, who unveiled a 9.1% stake in the micro-blogging website on April 4, was due to assume his seat on the board Saturday and had spoken publicly of his desire to bring “significant improvements” to the company. ‘Get Out the Popcorn Time’CEO Parag Agrawal said that Musk has “declined to join our board” …