[ixpmanager] public traffic graphs restricted in 6.0.0

[Marco d'Itri]

After the upgrade (which was otherwise smooth after I noticed that I had 
to double check all the skinned templates) the public traffic graphs now 
answer with a 401, did I miss something in the release notes?

https://manager.minap.it/grapher/ixp
https://manager.minap.it/grapher/ixp?id=1&type=png&period=day

root at manager:/srv/ixpmanager# grep ^GRAPHER_ .env
GRAPHER_BACKENDS="mrtg"
GRAPHER_CACHE_ENABLED=true
GRAPHER_BACKEND_MRTG_DBTYPE="rrd"
GRAPHER_BACKEND_MRTG_WORKDIR="/var/lib/mrtg/"
GRAPHER_BACKEND_MRTG_LOGDIR="/var/lib/mrtg/"
root at manager:/srv/ixpmanager#

-- 
ciao,
Marco