Fix broken variables in NativeLink Cloud CI jobs and disable RBE test

[bclark8923]

Description

Please include a summary of the changes and the related issue. Please also
include relevant motivation and context.

Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please also list any relevant details for your test configuration

Checklist

• Updated documentation if needed
• Tests added/amended
• bazel test //... passes locally
• PR is contained in a single commit, using git amend see some docs

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This change is 

[adam-singer]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: 1 of 1 LGTMs obtained, and all files reviewed, and pending CI: Publish image, Publish nativelink-worker-init, Publish nativelink-worker-lre-cc, and 1 discussions need to be resolved

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.github/workflows/main.yml line 63 at r1 (raw file):

          --remote_header=x-nativelink-project=nativelink-ci \
          --remote_executor=grpcs://scheduler-tracemachina-shared.build-faster.nativelink.net:443 \
          --remote_default_exec_properties="container-image=docker://$RBE_IMAGE" \

This is the most annoying github thing.. almost looks like a shell variable but isn't. ${RBE_IMAGE} doesn't work on github actions

[aaronmondal]

fyi we need to fix the hash mismatch outlined in nlewo/nix2container#150 to unblock this.

Reviewed all commit messages.
Reviewable status: 2 of 1 LGTMs obtained, and all files reviewed, and pending CI: Publish image, Publish nativelink-worker-init, Publish nativelink-worker-lre-cc, and 1 discussions need to be resolved

[aaronmondal]

Sent #1294 to fix the OCI workflow

[bclark8923]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! 2 of 1 LGTMs obtained, and all files reviewed