Error 500 in Admin dashboard when Geo is enabled and current node is not defined

Admin dashboard can become inaccessible (error 500) when Geo is enabled and current node is not defined in "GeoNode" table.

Geo "current_node" can be in three states: undefined, primary, secondary. We should handle all three states in the dashboard and make the same fix to rake gitlab:env:info output.

Ticket from client: https://gitlab.zendesk.com/agent/tickets/29488 cc @markglenfletcher