Fix error caused by all_reduce call in domino (#6880)
Fix #6851
Initialize communication backend to fix error caused by all_reduce call
in the Domino transformer layer.
Verified correctness in local test.
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Co-authored-by: Olatunji Ruwase <olruwase@microsoft.com>
Co-authored-by: Logan Adams <114770087+loadams@users.noreply.github.com>
