Historically we have collected devstack logs under /opt/stack.
Stop doing that and collect them in the stage_dir instead, so that
once the base job logs pull service comes around we are ready for it.
This add the benefit of writing things into a folder which is
already owned by the ansible user (ansible_user_dir), so we don't
run into issue writing there.
A few logs (devstack log, log summary and dstat) use to show up on
logs.o.o. just because they happened to already be in /opt/stack/logs.
With this change they would be lost, so adding them to post.yaml.
Depends-on: I5ad4dfccbc1389da3afc53f3c866d3475e006db6
Change-Id: Ib4be2f5056c0dc2b776de4a0d18b47b12624be92