container: T6218: fix host IPv6 link-local address for VRF networks (backport #3286)

[mergify]

Change Summary

Fix IPv6 EUI64 link-local address generation for host (pod-) interfaces assigned to a VRF.

Currently, container networks that are assigned to a VRF result in not having a valid IPv6 link-local address on the host. This is due to the address being assigned and then the VRF being changed resulting in the loss of the link-local address.

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/T6218

Related PR(s)

Component(s) name

• container

Proposed changes

Correct the ordering of the VRF assignment and link-local address generation logic. (Swap lines 476 and 477).

How to test

Create a container network that is assigned to any VRF other than default and ensure an IPv6 EUI64 link-local address is generated:

Configuration:

set container network TEST prefix '169.254.1.0/24'
set container network TEST prefix 'fd00:169:254:1::/64'
set container network TEST vrf TESTVRF
set container name SERVICE1 network TEST

Verification:

6: pod-SERVICES: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master SERVICE state UP group default qlen 1000
    link/ether 8a:61:51:a0:21:09 brd ff:ff:ff:ff:ff:ff
    inet 169.254.1.1/24 brd 169.254.1.255 scope global pod-SERVICES
       valid_lft forever preferred_lft forever
    inet6 fd00:169:254:1::1/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::8861:51ff:fea0:2109/64 scope link
       valid_lft forever preferred_lft forever

Smoketest result

N/A

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

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This is an automatic backport of pull request #3286 done by [Mergify](https://mergify.com).