Convert ringbuilder to build devices array

Convert ringbuilder to build devices array

Currently we have some hard-coded mangling in t-h-t but we
instead need to build the array based on the nodes running swift
storage, combined with the SwiftRawDisks parameter.

This will enable running SwiftStorage on nodes other than Controller
and SwiftStorage roles, and is required for custom-roles due to
the hard-coded stuff in the role templates and overcloud.yaml

Change-Id: I11deed1df712ecccf85d36a75b3bd2e9d226af36
Partially-Implements: blueprint custom-roles