xml: T5179: fix missed case in multi_to_list conversion

[jestabro]

Change Summary

The fix for multi_to_list in T3234 only handled the case of multiple XML elements in an interface-definition file sharing a single name at the same level; extend for the case of multiple sub-elements sharing a path of length > 1 at the same level, for example, after merging include files:

protocols-bgp.xml

will contain two instances of path ["address-family", "l2vpn-evpn"] under ["protocols", "bgp"].

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/T5179

Component(s) name

Proposed changes

How to test

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

[dmbaturin]

My only objection is too many S's in "misssed". :)

[jestabro]

Oops, yes; thanks !