lldp: T6727: add missing input validation for interface names (backport #4091)

[mergify]

Change Summary

There is no input CLI validation on the interface name passed to the LLDP service.

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/T6727

Related PR(s)

Component(s) name

lldp

Smoketest result

vyos@vyos:~$ /usr/libexec/vyos/tests/smoke/cli/test_service_lldp.py
test_01_lldp_basic (__main__.TestServiceLLDP.test_01_lldp_basic) ... ok
test_02_lldp_mgmt_address (__main__.TestServiceLLDP.test_02_lldp_mgmt_address) ... ok
test_03_lldp_interfaces (__main__.TestServiceLLDP.test_03_lldp_interfaces) ... ok
test_04_lldp_all_interfaces (__main__.TestServiceLLDP.test_04_lldp_all_interfaces) ... ok
test_05_lldp_location (__main__.TestServiceLLDP.test_05_lldp_location) ... ok
test_06_lldp_snmp (__main__.TestServiceLLDP.test_06_lldp_snmp) ... ok

----------------------------------------------------------------------
Ran 6 tests in 14.461s

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

---

This is an automatic backport of pull request #4091 done by [Mergify](https://mergify.com).

[github-actions]

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