This change adds a min_age parameter to the github CI SDK garbage
collector. The parameter specifies a minimum age (in days) for artifacts
to be garbage collected. NOTE that this can result in more artifacts
being kept than specified via the "keep" parameter if artifacts are
younger than min_age.
The change also has garbage_collect.sh pass the min_age parameter to
garbage_collect_github_ci_sdk.sh.
Signed-off-by: Thilo Fromm <thilofromm@microsoft.com>
