[QA] beta was not accepting login today

[Antoine Musso]

Hello,

It was no more possible to authenticate on the beta cluster from roughly
11:50am UTC till 18:50 UTC.

The root cause was a configuration change having a nasty side effect
which caused the backend storing the user sessions to no more be reachable.

Related tasks in order of investigation:

Cannot login on Commons Beta, complains about disabled cookies
https://phabricator.wikimedia.org/T127964

deployment-mediawiki02 lost memcached access at 11:51am UTC
https://phabricator.wikimedia.org/T127966

deployment-tin puppet Error 400 on SERVER: Failed to parse template
nutcracker/nutcracker.yml.erb
https://phabricator.wikimedia.org/T127845


That last one remains open. The service got restored via a workaround by
Giuseppe Lavagetto  (thank you!). A nicer solution is to be found.

I have retriggered a few browser tests.

-- 
Antoine "hashar" Musso