save metadata.json & common.py on local rank 0 on each node

[dimapihtar]

What does this PR do ?

Switched metadata.json & common.py writes from "global rank 0 only" to "local rank 0 on each node". Fix for: #1531

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[dimapihtar]

/ok to test abba529

[asolergi-nv]

Maybe I'm missing some context, but what is the motivation for this? 3 weeks ago in #1531 this was not necessary.

Have you tested this change with >1 nodes? With this changes now in lustre we will have many ranks saving those files in the same location, so we are fixing the setup mentioned in #1531 at the cost of regressing when using lustre...

[dimapihtar]

Closing this PR. Decided that fix is not relevant.