add debian-sid-jenkins
Trying to get the gerrit build job for osmo-upf to work,
for patch Ic0d319eb4f98cd51a5999c804c4203ab0bdda650
which adds use of nftables.
Maybe a newer debian version for the docker image may help.
Change-Id: Ieb4fb1ddee80315b547ea7e3405a56fcc41daaad
