Create quay.io/coreos-assembler/nfs

[jbtrystram]

I recently added a NFS server container, primarily for the kdump.crash.nfs

See #3917

I triggered the pipeline to build the image but it couldn't be published as quay.io/coreos-assembler/nfs does not exist.

This just needs to be created so I can re-add the NFS test and it should pass on all the arches then.

[jlebon]

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