Fix the weird bug in control_flow_op_test.py (#26931)
Summary:
In some version of python, then_net and else_net may switch the order. Let's make sure we are iterating the right arg node.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26931
Reviewed By: hl475
Differential Revision: D17614829
Pulled By: houseroad
fbshipit-source-id: 3f1b4eb91ecf4d808f58c34896d3e628aa2e0af0
