fix(xo-web/host/network): do not PIF.reconfigure_ipv6 if IPv6 is an empty string

[MathieuRA]

To test

On the nested pool: 172.16.210.181, try to reconfigure IPv4 of the management PIF on the host mra 8.2 slave.
On master: You can see an error in the web console. "INVALID_IP_ADDRESS_SPECIFIED"
On this branch: No error and IPv4 is reconfigured

Description

See https://team.vates.fr/vates/pl/utda1cc3p3roiknt5y4yn3xqjo
Introduced by 1becccf

Checklist

• Commit
  • Title follows commit conventions
  • Reference the relevant issue (Fixes #007, See xoa-support#42, See https://...)
  • If bug fix, add Introduced by
• Changelog
  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md
• PR
  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft

Review process

This 2-passes review process aims to:

• develop skills of junior reviewers
• limit the workload for senior reviewers
• limit the number of unnecessary changes by the author

1. The author creates a PR.
2. Review process:
   1. The author assigns the junior reviewer.
   2. The junior reviewer conducts their review:
      • Resolves their comments if they are addressed.
      • Adds comments if necessary or approves the PR.
   3. The junior reviewer assigns the senior reviewer.
   4. The senior reviewer conducts their review:
      • If there are no unresolved comments on the PR → merge.
      • Otherwise, we continue with 3.
3. The author responds to comments and/or makes corrections, and we go back to 2.

Notes:

1. The author can request a review at any time, even if the PR is still a Draft.
2. In theory, there should not be more than one reviewer at a time.
3. The author should not make any changes:
   • When a reviewer is assigned.
   • Between the junior and senior reviews.

[julien-f]

Do we know if this is a recent issue and which commit introduced it?