It doesn't matter who did. Yes, theoretically, both sides could have done it to blame it on the other side. That carries huge risks, though, and I'm not convinced either would accept those risks, simple as that.

There was nothing to gain, militarily or politically, from shooting the plane down.

So, the most reasonable conclusion is that it was a mistake, probably by the pro-Russian forces.

Don't see how it is relevant for this discussion, though.