Images prestaging fails due to missing pigz utility

[Tee Ngo]

Brief Description
-----------------
Subcloud prestage for upgrade failed in master (StarlingX 7.0) as the subcloud does not have pigz utility. This issue only occurs when the subcloud is running StarlingX 6.0 and has 4 or more cores assigned to Platform function.

Severity
--------
Major

Steps to Reproduce
------------------
Bring up a DC system with StarlingX 6.0. The AIOSX subclouds must have 4 (or more) platform cores.
Upgrade the system controller to StarlingX 7.0
Prestage the AIOSX subclouds for upgrade

Expected Behavior
------------------
AIOSX subclouds are prestaged successfully

Actual Behavior
----------------
Prestage failed for all AIOSX subclouds as pigz utility is not included in the image.

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

System Configuration
--------------------
Distributed Cloud

Branch/Pull Time/Commit
-----------------------
May 28th master build

Last Pass
---------
First time testing subcloud prestage for upgrade in StarlingX 7.0

Timestamp/Logs
--------------
TASK [prestage/prestage-images : Generate image bundles] ***********************
Saturday 11 June 2022 16:59:17 +0000 (0:00:09.964) 0:05:32.783 *********
fatal: [subcloud2001]: FAILED! => changed=true
msg: non-zero return code
rc: 127
stderr: |-
Shared connection to 2620:10a:a001:d41::124 closed.
stderr_lines:

Shared connection to 2620:10a:a001:d41::124 closed.
stdout: |2-
Building archive...
/tmp/.ansible-sysadmin/tmp/ansible-tmp-1654966757.46-93512383016271/gen-image-bundles.sh: line 53: pigz: command not found

Test Activity
-------------
Developer Testing

Workaround
----------
Reduce the number of platform cores on the subcloud to bypass the error

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/ansible-playbooks/+/845538

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/ansible-playbooks/+/845538
Committed: https://opendev.org/starlingx/ansible-playbooks/commit/f7dfea4e191d3a9dd6d78315d505bfe03d213885
Submitter: "Zuul (22348)"
Branch: master

commit f7dfea4e191d3a9dd6d78315d505bfe03d213885
Author: Tee Ngo <email address hidden>
Date: Mon Jun 13 00:56:29 2022 -0400

    Add check for the existence of pigz utility

    The usage of pigz was introduced in commit
    https://review.opendev.org/c/starlingx/ansible-playbooks/+/837592.
    As this utility is only included in StarlingX 7.0 image,
    subclouds running StarlingX 6.0 would fail to prestage. The
    solution is to check for the existence of pigz utility besides
    the number of platform cores before using it.

    Test Plan:
      - Verify that prestage works for both reinstall and upgrade
        use cases with system controller running StarlingX 7.0

    Closes-Bug: 1978442
    Change-Id: I656df2ceaed0afe11ce73eff04a949f865754fb0
    Signed-off-by: Tee Ngo <email address hidden>