[Entity Analytics] Fix flickering "Enable risk engine" button (#204486)

## Summary

When we refetch the engine status, the enable component was flickering,
I have changed it so we only load on the first request, after that we
keep displaying the "stale" value while the request is fetching.

Here is the flicker, blink and you'll miss it!



https://github.com/user-attachments/assets/5271674c-1534-470a-996f-058afd5ed76f

x-pack/solutions/security/plugins/security_solution/public/entity_analytics/components/risk_score_enable_section.tsx

@@ -289,7 +289,7 @@ export const RiskScoreEnableSection: React.FC<{
                 <RiskEngineStatusRow
                   currentRiskEngineStatus={currentRiskEngineStatus}
                   onSwitchClick={onSwitchClick}
-                  isLoading={isLoading}
+                  isLoading={isLoading && !currentRiskEngineStatus}
                   privileges={privileges}
                 />
               )}