Failed to update stx.5.0 layered build urls

[Scott Little]

Brief Description
-----------------
stx 5.0 is seeing build failures that have been traced back to a failure
to update layered build urls for rc/5.0

Severity
--------
critical

Steps to Reproduce
------------------
download_mirror.sh

Expected Behavior
------------------
Download the artifacts from stx 5.0 lower layer builds

Actual Behavior
----------------
Downloads the artifacts from stx master lower layer builds

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

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

Branch/Pull Time/Commit
-----------------------
May 3

Last Pass
---------
Never

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

Test Activity
-------------
Build

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

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: r/stx.5.0
Review: https://review.opendev.org/c/starlingx/tools/+/789378

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/tools/+/789378
Committed: https://opendev.org/starlingx/tools/commit/d1a4b4e8c24e4bc3e88a84d8305abccdd4c9f2f0
Submitter: "Zuul (22348)"
Branch: r/stx.5.0

commit d1a4b4e8c24e4bc3e88a84d8305abccdd4c9f2f0
Author: Scott Little <email address hidden>
Date: Mon May 3 11:45:13 2021 -0400

    Set layer build urls for stx 5.0

    On the new STX 5.0 branch, the urls for lower layer build
    artifacts were left pointing to the master build branch.

    This update fixes those urls.

    Closes-Bug: 1926984
    Signed-off-by: Scott Little <email address hidden>
    Change-Id: I846c7a03001abaecede1f85099254c1486b995be

[Ghada Khalil (gkhalil)]

Marking as Fix Released. The fix is specific to the r/stx.5.0 branch only.