Fix error caused by all_reduce call in domino

[hwchen2017]

Fix #6851
Initialize communication backend to fix error caused by all_reduce call in the Domino transformer layer.
Verified correctness in local test.

[GuanhuaWang]

thx @hwchen2017 please find comments

[hwchen2017]

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[GuanhuaWang]

let's see if the OOM error still exists in our CI test nv-torch-latest-v100