change latest_only to latest-only for consistency

still accepts latest_only for backward compatiblity but emits a warning

Change-Id: I007d2fa2e02f15a9fd4a2eebcf5883091c8b865b
Reviewed-on: https://review.openstack.org/31449
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins
fix invalid yaml in archive example

Change-Id: I9b10a33bafdc7d4811807ff01a96f37d9343b3c6
Reviewed-on: https://review.openstack.org/32643
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins