Update llama2-model.libsonnet to setup env with common.libsonnet

[ManfeiBai]

Description

Please include a summary of relevant context/issue and your changes.

Tests

Please describe the tests that you ran on TPUs to verify changes.

Instruction and/or command lines to reproduce your tests:
./scripts/run-oneshot.sh -t pt-nightly-llama2-pjrt-train-spmd-func-v4-8-1vm-1vm
./scripts/run-oneshot.sh -t pt-nightly-llama2-pjrt-infer-func-v4-8-1vm-1vm

List links for your tests (use go/shortn-gen for any internal link):
./scripts/run-oneshot.sh -t pt-nightly-llama2-pjrt-train-spmd-func-v4-8-1vm-1vm: http://shortn/_SfQAvt7dbI
./scripts/run-oneshot.sh -t pt-nightly-llama2-pjrt-infer-func-v4-8-1vm-1vm: http://shortn/_StagYnH5nx

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run one-shot tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed.

[vanbasten23]

LGTM

[vanbasten23]

I couldn't see the merge button. So you need to find someone who has the permission to merge it.

[ManfeiBai]

I couldn't see the merge button. So you need to find someone who has the permission to merge it.

thanks, Xiongfei, merged now