T5446: BGP: change <bgp paramater bestpath med> from node to leafNode

[nicolas-fort]

Change Summary

Change set protocols bgp paramater bestpath med from node to leafNode, in order to avoid empty value and problems when removing such parameters

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/T5446

Component(s) name

bgp

Proposed changes

How to test

vyos@LEFT# run show config comm | grep bgp
set protocols bgp address-family ipv4-unicast network 192.0.2.0/24
set protocols bgp neighbor 198.51.100.2 address-family ipv4-unicast soft-reconfiguration inbound
set protocols bgp neighbor 198.51.100.2 remote-as 'external'
set protocols bgp neighbor 198.51.100.2 update-source '198.51.100.1'
set protocols bgp parameters bestpath med 'missing-as-worst'
set protocols bgp parameters bestpath med 'confed'
set protocols bgp parameters router-id '198.51.100.1'
set protocols bgp system-as '65545'
[edit]
vyos@LEFT# sudo vtysh -c "show run" | grep med
 bgp bestpath med confed missing-as-worst
[edit]
vyos@LEFT# del protocols bgp parameters bestpath med confed 
[edit]
vyos@LEFT# commit
[edit]
vyos@LEFT# sudo vtysh -c "show run" | grep med
 bgp bestpath med missing-as-worst
[edit]
vyos@LEFT# del protocols bgp parameters bestpath med 
[edit]
vyos@LEFT# compare
[protocols bgp parameters bestpath]
- med "missing-as-worst"

[edit]
vyos@LEFT# commit
[edit]
vyos@LEFT# sudo vtysh -c "show run" | grep med
[edit]
vyos@LEFT# run show config comm | grep bgp
set protocols bgp address-family ipv4-unicast network 192.0.2.0/24
set protocols bgp neighbor 198.51.100.2 address-family ipv4-unicast soft-reconfiguration inbound
set protocols bgp neighbor 198.51.100.2 remote-as 'external'
set protocols bgp neighbor 198.51.100.2 update-source '198.51.100.1'
set protocols bgp parameters bestpath
set protocols bgp parameters router-id '198.51.100.1'
set protocols bgp system-as '65545'
[edit]
vyos@LEFT# 

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