T6523: Telegraf use nft scripts only if the firewall configured

[sever-sever]

Change Summary

If a firewall is not configured, there is no reason to get and execute telegraf firewall custom scripts as there are no nft chain in the firewall nftables configuration

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/T6523

Related PR(s)

Component(s) name

telegraf

Proposed changes

How to test

Before the fix, there was unexpected message:

vyos@r1-right# set service monitoring telegraf prometheus-client 
[edit]
vyos@r1-right# commit
[ service monitoring telegraf ]
nft table ip vyos_filter not found

[edit]
vyos@r1-right#

After the fix:

vyos@r1-right# set service monitoring telegraf prometheus-client 
[edit]
vyos@r1-right# commit
[edit]
vyos@r1-right# 

Smoketest result

vyos@r1-right:~$ /usr/libexec/vyos/tests/smoke/cli/test_service_monitoring_telegraf.py
test_01_basic_config (__main__.TestMonitoringTelegraf.test_01_basic_config) ... ok
test_02_loki (__main__.TestMonitoringTelegraf.test_02_loki) ... ok

----------------------------------------------------------------------
Ran 2 tests in 11.434s

OK
vyos@r1-right:~$

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]

👍 VyOS CLI smoketests finished successfully!

[c-po]

@Mergifyio backport circinus

[mergify]

backport circinus

✅ Backports have been created

• #3751 T6523: Telegraf use nft scripts only if the firewall configured (backport #3748) has been created for branch circinus

[sever-sever]

@Mergifyio backport sagitta

[mergify]

backport sagitta

✅ Backports have been created

• #3826 T6523: Telegraf use nft scripts only if the firewall configured (backport #3748) has been created for branch sagitta