false missing tarball in log_download_tarball_missing.txt

[Scott Little]

Brief Description
-----------------
After download_mirror.sh, the log_download_tarball_missing.txt contained a
false log of a download failure. The log of a prior download failure was
not cleared as part of the latest download attempt.

Severity
--------
Minor

Steps to Reproduce
------------------
1) inject a fake missing file report into ...
stx-tools/centos-mirror-tools/logs/log_download_tarball_missing.txt
2) rund download_mirrors.sh
3) inspect stx-tools/centos-mirror-tools/logs/log_download_tarball_missing.txt to
see if the previous log was cleared

Expected Behavior
------------------
log_download_tarball_missing.txt reports only failures from the most recent download attempt.

Actual Behavior
----------------
Historical failures are never cleared from log_download_tarball_missing.txt.

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

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

Branch/Pull Time/Commit
-----------------------
N/A day one?

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

Timestamp/Logs
--------------
logs/log_download_tarball_missing.txt:https://s3.amazonaws.com/chartmuseum/release/v0.12.0/bin/linux/amd64/chartmuseum

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

Workaround
----------
manually delete stx-tools/centos-mirror-tools/logs/log_download_tarball_missing.txt prior to a new run of download_mirrors.sh

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/tools/+/790809

[Ghada Khalil (gkhalil)]

screening: low; minor build issue

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/tools/+/790809
Committed: https://opendev.org/starlingx/tools/commit/3731971b9888aae1d87b68904372048f5f6df077
Submitter: "Zuul (22348)"
Branch: master

commit 3731971b9888aae1d87b68904372048f5f6df077
Author: Scott Little <email address hidden>
Date: Tue May 11 15:18:08 2021 -0400

    clear log_download_tarball_missing.txt

    The records of prior download failures are never being cleared
    from log_download_tarball_missing.txt.

    log_download_tarball_missing.txt needs to be cleared at the start of
    each new download attempt.

    Closes-bug: 1928131
    Signed-off-by: Scott Little <email address hidden>
    Change-Id: Id38b49f8d7d8ab7c31e54d70fad097dd806f2dd5