[QA] Merging CI configuration repos

[Antoine Musso]

Hello,

We define Jenkins jobs using Jenkins Job Builder and have the resulting
job triggered by Zuul.  For historical reasons, the configuration files
for each are held in two different repositories:

 integration/jenkins-job-builder-config.git
 integration/zuul-config.git

C. Scott proposed a few weeks ago to merge them both which is definitely
a good idea (less commit / reviews have to be made).


To be able to keep the git history and ease merging, I am proposing to
move the configuration files to a subdirectory, respectively under:

 /jjb/
 /zuul/

Then update:
* jobs triggered on each repositories needs some path to be adjusted
* the Zuul daemon refers to /etc/zuul/wikimedia/layout.yaml


Once done, will merge both repositories into a new
integration/config.git which will have the full history and the two
directory

* documentation update


Thoughts?

-- 
Antoine "hashar" Musso