syslog: T6989: fix typos and add option to disable MARK

[c-po]

Change summary

Fix CLI validator and error message for marker interval.
Add possibility to disable the mark module.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T6989

Related PR(s)

• syslog: T6989: convert old configuration format to "advanced" #4305
• syslog: T6989: add CLI command to disable periodic injection of mark messages vyos-documentation#1604

How to test / Smoketest result

vyos@vyos:~$ /usr/libexec/vyos/tests/smoke/cli/test_system_syslog.py
test_basic (__main__.TestRSYSLOGService.test_basic) ... ok
test_console (__main__.TestRSYSLOGService.test_console) ... ok
test_remote (__main__.TestRSYSLOGService.test_remote) ... ok
test_vrf_source_address (__main__.TestRSYSLOGService.test_vrf_source_address) ... ok

----------------------------------------------------------------------
Ran 4 tests in 10.833s

OK

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[github-actions]

👍
No issues in PR Title / Commit Title

[github-actions]

CI integration ❌ failed!

Details

CI logs

• CLI Smoketests (no interfaces) ❌ failed
• CLI Smoketests (interfaces only) ❌ failed
• Config tests 👍 passed
• RAID1 tests 👍 passed
• TPM tests 👍 passed