Enable per-role SchedulerHints

Enable per-role SchedulerHints

This adds a parameter for each role, where optional scheduler hints
may be passed to nova.  One potential use-case for this is using
the ComputeCapabilities to pin deployment to a specific node (not
just a specific role/profile mapping to a pool of nodes like we
have currently documented in the ahc-match docs).

This could work as follows:

1. Tag a specific node as "node:controller-0" in Ironic:

ironic node-update <id> replace properties/capabilities='node:controller-0,boot_option:local'

2. Create a heat environment file which uses %index%

parameters:
  ControllerSchedulerHints:
    'capabilities:node': 'controller-%index%'

Change-Id: I79251dde719b4bb5c3b0cce90d0c9d1581ae66f2