Normalize slave ulimits and cgroups.

Make the slave ulimits and cgroups settings consistent across all slave
platforms. This means enabling ulimits and cgroups on all oneiric static
slaves.

Change-Id: If02b54d2e4fa04646f55f8a4530cea8cc2f4f275
Reviewed-on: https://review.openstack.org/23107
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