Fix local_cache in multi_returner

[a76yyyy]

What does this PR do?

Fixes incorrect storage of _return-type job results in local_cache when using multi_returner configuration. Now strictly follows the logic in salt.utils.job.store_job by only executing multi-returner storage when load['cmd'] is not equal to '_return'.

What issues does this PR fix or reference?

None

Previous Behavior

With multi-returner configuration:

master_job_cache: multi_returner
multi_returner:
  - local_cache
  - elasticsearch # or other

All types of return data (including cmd: _return job results) were stored in local_cache, violating the expected behavior defined in store_job logic:

salt/salt/utils/job.py

Lines 127 to 130 in f906ca5

	save_load = True
	if job_cache == "local_cache" and mminion.returners[getfstr](load.get("jid", "")):
	# The job was saved previously.
	save_load = False

New Behavior

Now only save_load when returner_ == "local_cache" and load['cmd'] != '_return'

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

No

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[twangboy]

Please add a changelog and some tests

[twangboy]

Please write a test for this

[dwoz]

Please write a test for this

@a76yyyy