I doubt it was intentional. They had shot down a Ukrainian cargo plane earlier in the week along with two fighters. They were just maintaining air control over the territory occupied by the pro-Russian insurgents. In war, sh*t happens. No doubt operational control was lax. It would be interesting to learn how far up the command chain the guys in charge of the missile battery had to go to get permission to launch.
There is no way to mistake a commercial jet flying at 33,000 feet still climbing as it is 5 minutes from passing out of your air space for a Ukrainian transport plane that would have to be dropping altitude and slowing down in preparation for landing.