fix(ray): Use default svc account if not set in task metadata

[pingsutw]

Tracking issue

NA

Why are the changes needed?

The default service account is not being used if autoscale is enabled in the ray task.

What changes were proposed in this pull request?

Use default service account in the config if it's not being set.

How was this patch tested?

sandbox

Setup process

config = RayJobConfig(
    worker_node_config=[WorkerNodeConfig(group_name="test_group", replicas=3, min_replicas=0, max_replicas=10)],
    runtime_env={"pip": ["numpy"]},
    enable_autoscaling=True,
    shutdown_after_job_finishes=True,
    ttl_seconds_after_finished=20,
)

Screenshots

Check all the applicable boxes

• [x] I updated the documentation accordingly.
• [x] All new and existing tests passed.
• [x] All commits are signed-off.

Related PRs

NA

Docs link

NA

[pingsutw]

cc @EngHabu @hamersaw @fiedlerNr9

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 60.99%. Comparing base (c10346d) to head (417a3a3).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5499 +/- ## ========================================== - Coverage 61.01% 60.99% -0.03% ========================================== Files 794 794 Lines 51441 51443 +2 ========================================== - Hits 31388 31378 -10 - Misses 17161 17172 +11 - Partials 2892 2893 +1 ``` | [Flag](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | Coverage Δ | | |---|---|---| | [unittests-datacatalog](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `69.31% <ø> (ø)` | | | [unittests-flyteadmin](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `58.67% <ø> (-0.07%)` | :arrow_down: | | [unittests-flytecopilot](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `17.79% <ø> (ø)` | | | [unittests-flytectl](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `68.03% <ø> (-0.06%)` | :arrow_down: | | [unittests-flyteidl](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `79.04% <ø> (ø)` | | | [unittests-flyteplugins](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `61.85% <100.00%> (+<0.01%)` | :arrow_up: | | [unittests-flytepropeller](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `57.30% <ø> (ø)` | | | [unittests-flytestdlib](https://app.codecov.io/gh/flyteorg/flyte/pull/5499/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `65.82% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg#carryforward-flags-in-the-pull-request-comment) to find out more.

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