OpenCloud reads var_opencloud_${server}_fqdn for each server in
servers=("opencloud" "collabora" "wopi"), so the scan for literal
var_ names found nothing and the build stopped at the first prompt
(#18586). Templates of the form var_...${x}... are now expanded with
the words of `for x in ...`, or of the array that loop walks; nothing
is executed. Hostname-like answers are derived from the variable name
(ci-opencloud-collabora.example.test), so several cannot collide.