Centos 8.4 release requires repo definition adjustments to avoid build failures

[Rafael Lucas Camargos]

Brief Description
-----------------
Centos 8.4 released.
Centos 8.3 will likely be moving to the vault.
Adjust StarlingX repo definitions accordingly to prevent
package build failures.

Severity
--------
Major

Steps to Reproduce
------------------
N/A

Expected Behavior
------------------
N/A

Actual Behavior
----------------
N/A

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

System Configuration
--------------------
N/A

Branch/Pull Time/Commit
-----------------------
Sep 13 2021

Last Pass
---------
Sep 06 2021

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

Test Activity
-------------
N/A

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

[Rafael Lucas Camargos (rcamargo)]

Relates to https://bugs.launchpad.net/starlingx/+bug/1907281

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/tools/+/808962

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/tools/+/808962
Committed: https://opendev.org/starlingx/tools/commit/3fbb1699377047ab7415f96ae7f86de4795401d4
Submitter: "Zuul (22348)"
Branch: master

commit 3fbb1699377047ab7415f96ae7f86de4795401d4
Author: Scott Little <email address hidden>
Date: Tue Sep 14 09:58:37 2021 -0400

    Centos 8.4 released, 8.3 moves to vault

    Closes-Bug: 1943498
    Signed-off-by: Scott Little <email address hidden>
    Change-Id: I6c40a1c940d6ca9003dcea496a8b88cad1e334a9

[Scott Little (slittle1)]

fixed on master by https://review.opendev.org/c/starlingx/tools/+/808962