[JIT] Always map node output in vmap (#43988)
Summary:
Previously when merging a node without a subgraph, we would merge the node's outputs to the corresponding subgraph values, but when merging a node with a subgraph the node's outputs would be absent in the value mapping. This PR makes it so they are included.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43988
Reviewed By: ZolotukhinM
Differential Revision: D23462116
Pulled By: eellison
fbshipit-source-id: 232c081261e9ae040df0accca34b1b96a5a5af57
