Eng 6452 inline agg join

It seems silly/wasteful to be cloning an outputschema for the inline limit:
1) It is probably not used, so maybe it could be just set to null?
2) If null is a problem, the referenced outputschema is very probably not modified, so a simple assignment would be OK here.
3) If the correctness of the outputschema really mattered in any way, the preagg outputschema would be the wrong choice.