[AWS] Add check for empty values in elasticache module - fixes #40063 (#40454)

lib/ansible/modules/cloud/amazon/elasticache.py

@@ -369,7 +369,7 @@ class ElastiCacheManager(object):
             'EngineVersion': self.cache_engine_version
         }
         for key, value in modifiable_data.items():
-            if value is not None and self.data[key] != value:
+            if value is not None and value and self.data[key] != value:
                 return True
 
         # Check cache security groups