The big-screen adaptation of HBO’s now-defunct series “Entourage,” hoping to repeat the silver-screen success of “Sex and the City,” opened in movie theaters last Wednesday and over the weekend, and star Kevin Dillon celebrated by hosting Saturday afternoon at Rehab in the Hard Rock Hotel Las Vegas. Even with the thermometer in the toasty 90s, Dillon showed up in a gray T-shirt, faded jeans and bowling-style dress shoes with gray socks.