Split out BootstrapNode SoftwareConfig

Split out BootstrapNode SoftwareConfig

This patch splits out the BootstrapNode config
such that alternate implementation (puppet for example)
can implement their own SoftwareConfig's via a nested stack.

This is controlled by the standard overcloud heat environment.

For os-apply-config deployments the implementation should work the
same as before.

For puppet deployments the implementation uses hiera metadata
to configure bootstrap_nodeid.

Change-Id: I691a9d7c474866038a5d47beab295899b5479d03