[Featured][systemd] Generated service should not be enabled in featured

[mlok-nokia]

Why I did it

On multiasic platform, with Trixie, there will be services that will be defined in /run/systemd/generator as "generatad" UnitFileState. Such as PMON, SNMP, radv and other are generated service. Enabling such services fails because it's assumed to be always enabled. This PR modifies the featured to skip enabling the generated services. Fix issue sonic-net/sonic-buildimage#25414

Work item tracking

• Microsoft ADO (number only):

How I did it

Featured always enabled the service files based on the configuration of the feature table. This PR add code to check is UnitFileState is generated, skip and not append the "systemctl enable " command to the cmds list.

How to verify it

bootup the new image in the multiasic platform, the following log should not be seen in the syslog:

2026 Feb  4 05:37:49.443422  sonic ERR featured: ['sudo', 'systemctl', 'enable', 'eventd.service'] - failed: return code - 1, output:              
2026 Feb  4 05:37:55.587767 sonic ERR featured: ['sudo', 'systemctl', 'enable', 'pmon.service'] - failed: return code - 1, output:             
2026 Feb  4 05:37:58.027168 soinc ERR featured: ['sudo', 'systemctl', 'enable', 'radv.service'] - failed: return code - 1, output:
2026 Feb  4 05:40:41.483658 sonic ERR featured: ['sudo', 'systemctl', 'enable', 'gnmi.service'] - failed: return code - 1, output:              
2026 Feb  4 05:40:49.039632 sonic ERR featured: ['sudo', 'systemctl', 'enable', 'mgmt-framework.service'] - failed: return code - 1, output:              
2026 Feb  4 05:40:51.358646 sonic ERR featured: ['sudo', 'systemctl', 'enable', 'snmp.service'] - failed: return code - 1, output:

Which release branch to backport (provide reason below if selected)

• 202305
• 202311
• 202405
• 202411
• 202505
• 202511

[mssonicbld]

This PR has backport request for branch(es): 202511.
Added label(s) for branch(es) 202511.

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[yijingyan2]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[abdosi]

@anamehra : please sign-off if this looks good.

[anamehra]

@anamehra : please sign-off if this looks good.

I will take a look. Thanks

[anamehra]

LGTM, need test coverage.

[anamehra]

This behavior looks fine functionally: generated units should not be enabled, and this still keeps the start path intact. Could you add one targeted unit test in tests/featured/featured_test.py for enable_feature() with get_systemd_unit_state() returning generated, asserting unmask and start are called but no systemctl enable command is issued?