8344361: Restore null return for invalid services from legacy providers

Reviewed-by: valeriep

src/java.base/share/classes/java/security/Provider.java

@@ -1147,6 +1147,7 @@ public abstract class Provider extends Properties {
             s = legacyMap.get(key);
             if (s != null && !s.isValid()) {
                 legacyMap.remove(key, s);
+                return null;
             }
         }