This update for opensuse-leap-image fixes the following issues:

- Add curl (jsc#SLE-23748) and timezone (boo#1201537)
- Add zypper explicitly to work around obs-build bug
(gh#openSUSE/obs-build#562)
- Add org.opencontainers.image.source label
- Clean /var/log and /var/cache/zypp
- Remove /var/log/lastlog to avoid container size explosion
- Remove zypp's AnonymousUniqueId explicitly. kiwi does that,
but better be sure.