Updated openstack/openstack
Project: openstack/heat  88853d5d9de1deaac9354b2d523bd14a488c0639

Re-enable doc generation for contrib plugins

This re-enables doc generation for contrib plugins and removes legacy
code no longer needed because of stevedore.

Related-Bug: 1403897
Change-Id: Ia51cb7c8b0c375d2a430d45b9ece50eb67271788