Use overcloud-full instead of atomic-image

Use overcloud-full instead of atomic-image

This switches to using overcloud-full as the OS image for
containerized compute. It includes the following changes:
- install docker, until this change lands
  I1eab2a6de721c8f3c21c7df0019f2d4d1cc3775f
- agent image pull has been removed. This avoids a race between docker
  starting and the current call to pull. This relies on "docker run"
  to do the initial pull and leaves open the option of some other
  prefetch mechanism to do the initial pull
- rely on unit Conflicts= to ensure heat-docker-agents and
  os-collect-config do not run at the same time
- tweaks to host bind mounts
- removal of commands which only apply to atomic

Co-Authored-By: Martin André <m.andre@redhat.com>
Change-Id: I2e82634785834a877a4dbdbdcd788a9ac1c14a9d