test: allow root user to be named "Super User"
test: allow root user to be named "Super User"

fedora-coreos recently changed the "real name" of the root user to
"Super User".  Allow that as a valid value.

cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit