[Sharing-NG] multiple mount request for items is allowed

[S-Panta]

Describe the bug

Once an item is mounted via API, it retuns 201 status code as specified in swagger with body content of drive item. But, hitting API a second time, it still returns 201 status code but nothing get returned in body

Steps to reproduce

1.Login to ocis as admin
2.create a folder test and share to einstein
3. click disable sync.
4. Send API request to mount resource

curl -X POST 'https://host.docker.internal:9200/graph/v1beta1/drives/{share-Space-Id}/root/children'  
-d '{
    "remoteItem": {
        "id":"'123"
    }
}' -ueinstein:relativity

5. It will mount the item. Send API request again

Actual behavior

The status code is 201 with empty body

Same is true while unmounting resource.

[S-Panta]

@rhafer

[2403905]

Fixed by PR the #8817