Pass RoleData into -post.yaml stacks

Pass RoleData into -post.yaml stacks

This patch modifies the interface for the -post stacks so
that we pass RoleData instead of just the StepConfig
into each -post.yaml template.

This will facilitate creating other types of -post.yaml scripts
that require more data that just 'step_config'. Things like
containers, etc. will require this.

Change-Id: I2527fc0098192f092f5e9046033a04bc71be2cae