irqbalance: Tweak irqbalance environment file to squelch systemd warning

Merge Checklist

All boxes should be checked before merging the PR (just tick any boxes which don't apply to this PR)

[x] The toolchain has been rebuilt successfully (or no changes were made to it)
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[x] Any updated packages successfully build (or no packages were changed)
[x] Packages depending on static components modified in this PR (Golang, *-static subpackages, etc.) have had their Release tag incremented.
[x] Package tests (%check section) have been verified with RUN_CHECK=y for existing SPEC files, or added to new SPEC files
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[x] All source files have up-to-date hashes in the *.signatures.json files
[x] sudo make go-tidy-all and sudo make go-test-coverage pass
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[x] Ready to merge

Summary

What does the PR accomplish, why was it needed? Our 3.0 images produce some extra noise during boot: irqbalance: "Referenced but unset environment variable evaluates to an empty string: IRQBALANCE_ARGS"

This is due to the variable IRQBALANCE_ARGS, referenced in irqbalance.service, not being defined in the EnvironmentFile pointed to by that service. Sed the Environment file to uncomment IRQBALANCE_ARGS, explicitly setting it to the empty string.

Change Log

Sed the Environment file for irqbalance to uncomment IRQBALANCE_ARGS, explicitly setting it to the empty string

Does this affect the toolchain?

Test Methodology

Buddy build: https://dev.azure.com/mariner-org/mariner/_build/results?buildId=597498&view=results

microsoft / azurelinux