Nah, if they intended to shoot down their own plane, they'd have tried to pin the blame on the US from the start. They could've easily tried to claim that the US sent a drone in to shoot the plane down, but they didn't.

Them going with the "mechanical problem" off the bat indicates that they were caught totally off guard and their unwillingness to hand over the black box supports them wanting to save face. The first casualties of their war with the US are their own citizens killed by their own bumbling idiocy.