[QA] integration/config changes no more need rebases

[Antoine Musso]

Hello,

Changes made to integration/config required to be fast forward only.

I have finally made Gerrit to attempt a rebase for us and allow content
to be transparently merged.

>From now on when one CR+2 and tests pass, Gerrit will automatically
rebase the change and merge it.  Thus we no more need to manually rebase
every single time a change is not on tip of branch.
That also let us CR+2 several changes in a row and CI does the right
thing: they get all merged.

Task for reference:
https://phabricator.wikimedia.org/T131008

-- 
Antoine "hashar" Musso