[Bug]: the db without permission can view the data from the first search iterator of the previous db

[qixuan0212]

Is there an existing issue for this?

• I have searched the existing issues

Environment

- Milvus version: master-20250105-7128e36e-amd64
- Deployment mode(standalone or cluster): both
- MQ type(rocksmq, pulsar or kafka): pulsar
- SDK version(e.g. pymilvus v2.0.0rc2): 2.6.0rc49
- OS(Ubuntu or CentOS): 
- CPU/Memory: 
- GPU: 
- Others:

Current Behavior

1. defaultDB - colA， db1 - colA
2. self.create_user(client_root, user_name=user_name, password=password)
   self.create_role(client_root, role_name=role_name)
   self.grant_role(client_root, user_name=user_name, role_name=role_name)
   self.grant_privilege(client_root, role_name, "Collection", "Search", collection_name, "default")
   self.grant_privilege(client_root, role_name, "Collection", "Insert", collection_name, "db1")
   client, _ = self.init_milvus_client(uri=uri, user=user_name, password=password)
3. db1 - colA search iterator
4. using_database(client, db1)
5. first search_iterator.next success

Expected Behavior

first search_iterator.next no permission

Steps To Reproduce

1. defaultDB - colA， db1 - colA
2. 
self.create_user(client_root, user_name=user_name, password=password)
self.create_role(client_root, role_name=role_name)
self.grant_role(client_root, user_name=user_name, role_name=role_name)
self.grant_privilege(client_root, role_name, "Collection", "Search", collection_name, "default")
self.grant_privilege(client_root, role_name, "Collection", "Insert", collection_name, "db1")
client, _ = self.init_milvus_client(uri=uri, user=user_name, password=password)
3. db1 - colA search iterator
4. using_database(client, db1)
5. first search_iterator.next

Milvus Log

https://grafana-4am.zilliz.cc/explore?orgId=1&panes=%7B%22knx%22:%7B%22datasource%22:%22vhI6Vw67k%22,%22queries%22:%5B%7B%22refId%22:%22A%22,%22expr%22:%22%7Bcluster%3D%5C%22devops%5C%22,namespace%3D%5C%22chaos-testing%5C%22,pod%3D~%5C%22searchiterator-v2-qx-hfghv.%2A%5C%22%7D%22,%22datasource%22:%7B%22type%22:%22loki%22,%22uid%22:%22vhI6Vw67k%22%7D%7D%5D,%22range%22:%7B%22from%22:%221736414582789%22,%22to%22:%221736414680339%22%7D%7D%7D&schemaVersion=1

Anything else?

N/A

[PwzXxm]

/assign

[PwzXxm]

wait for #39045 #39087 on query iterator fixed first.