When installing controller-1 through pxe, mgmt ip can't receive through dhcp.

[Joohyun]

Brief Description
-----------------
In case of IPv6 in AIO-DX, when installing controller-1 through pxe, the mgmt ip(no vlan) can't receive through dhcp. Therefore, can't communicate with controller-0 and fail to install.

Severity
--------
Major

Steps to Reproduce
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1. Install controller-0 using ipv6. (mgmt interface - no vlan)
2. Install controller-1 through pxe.

Expected Behavior
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Allocates ip to the mgmt interface through dhcp and succeed to install.

Actual Behavior
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The mgmt ip can't receive through dhcp.

Reproducibility
---------------
100%

System Configuration
--------------------
All

Branch/Pull Time/Commit
-----------------------
N/A

Last Pass
---------
N/A

Timestamp/Logs
--------------
N/A

Test Activity
-------------
Sanity

Workaround
----------
N/A

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/metal/+/851481

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Joohyun <email address hidden>" on branch: master
Review: https://review.opendev.org/c/starlingx/metal/+/851481