Move Redmine to a new virtualization host

Originally created by @intrigeri on #15919 (Redmine)

We have to move out of the obsolete virtualization setup where our Redmine is currently hosted, worst case by the end of the Jessie LTS support (2020-06-30) but I think we’re going to be expelled earlier than that.

Our options are:

• install a fresh VM hosted by Riseup, redo the Redmine setup (and Puppetize it properly), copy the data
• install a fresh VM on lizard, redo the Redmine setup (and Puppetize it properly), copy the data
• copy the entire VM as-is to a new VM on lizard
• copy the entire VM as-is to a new VM somewhere else than on lizard

Related issues

• Has duplicate sysadmin#16035 (closed)