Also correctly finish "st2 execution tail" if user is directly tailing a child execution.
Also correctly finish "st2 execution tail" if user is directly tailing a
child execution.

Plexxi/st2,StackStorm/st2,nzlosh/st2,nzlosh/st2,Plexxi/st2,StackStorm/st2,Plexxi/st2,Plexxi/st2,StackStorm/st2,StackStorm/st2,nzlosh/st2,nzlosh/st2