shell: Fix rendering of access level indicator
shell: Fix rendering of access level indicator

The "proxy" property of the SuperuserIndicator was not updated in time
with a change to the "host" property since "componentDidUpdate" runs
after render.  Let's just keep the proxy up-to-date in "render"
itself.

Fixes #17467

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