Make the seed default to NODE_* sizes.
Make the seed default to NODE_* sizes.

The seed has the same memory and CPU needs as an undercloud, and we're
breaking on 2G VMs with amd64 - because the seed hasn't been scaled
consistently.

Change-Id: I78e607f447aae89555b2169551e55ef787855038

rdo-management/tripleo,rdo-management/tripleo