Comment 3 for bug 1926987

Reviewed: https://review.opendev.org/c/starlingx/tools/+/789389
Committed: https://opendev.org/starlingx/tools/commit/b96ebc83d859a4a7802a462504817ecec6182a7b
Submitter: "Zuul (22348)"
Branch: master

commit b96ebc83d859a4a7802a462504817ecec6182a7b
Author: Scott Little <email address hidden>
Date: Mon May 3 13:16:53 2021 -0400

    fix bad flockflock url

    download_mirror.sh fails due to a bad path containing
    ‘stx-tools/centos-mirror-tools/config/centos/flockflock’

    The path is constructed, and the trigger is when an EOL is missing
    from a centos_build_layer.cfg file, causing 'cat' to merge the last
    line of the offending file with the first line of the next file.

    Switch 'cat' to 'grep', which will always ensure an EOL is present.
    Along the way, we can filter out empty lines and comments.

    Closes-bug: 1926987
    Signed-off-by: Scott Little <email address hidden>
    Change-Id: I2404b3415f0f3e2f395c2bcb7a527aa01a488f61