“It’s good to hold onto something.” It’s a simple enough phrase, given early on from one veteran Russian cosmonaut on the International Space Station to a novice American astronaut there for the first time. It’s meant literally here: The newbie would do well to hold on to her surroundings as she acclimates to the weightlessness of space. When we hear it at the end of “I.S.S.,” though, it’ll mean something entirely different. The I.S.S. itself is meant to be an international symbol of cooperation, and “I.S.S.,” directed by Gabriela Cowperthwaite (best known for the 2013 documentary “Blackfish”)…