web: change node registration parameter order (#2607)

This change makes editing the generated command easier.
For example, after pasting into a terminal, the cursor position will be
near the username portion which requires editing.

integration/scenario.go

@@ -842,6 +842,7 @@ func (s *Scenario) runHeadscaleRegister(userStr string, body string) error {
 		return errParseAuthPage
 	}
 	key := keySep[1]
+	key = strings.SplitN(key, " ", 2)[0]
 	log.Printf("registering node %s", key)
 
 	if headscale, err := s.Headscale(); err == nil {