Tolerate gateway_mfr errors

[posterzh]

Issue

• Link: https://github.com/NebraLtd/hm-diag/issues/352
• Summary: Should not generate sentry errors when gateway_mfr is exited with a non-zero status.

How The status of gateway_mfr is still logged but it shouldn't be logged in ERROR level so that no sentry issue to be made.

Screenshots

References

Checklist

• [ ] Tests added
• [ ] Cleaned up commit history (rebase!)
• [ ] Documentation added
• [ ] Thought about variable and method names

[sonarcloud[bot]]

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0.0% Duplication

[posterzh]

@marvinmarnold @pritamghanghas I want to abandon this PR in favor of https://github.com/NebraLtd/hm-diag/pull/359.