[HotFix] /nodes/{nodeId}/content REST API fails for content created by a deleted user

HF needs to include MNT-20714 & MNT-20965 please.

Description:

A user creates a document in the repository.  Subsequently that user is deleted.  When a second user calls the REST API to 'update the content' of the document, the call returns a success but the document is not updated.
 
Steps to reproduce:
 
1/. Install OOTB ACS v5.2.4.3
2/. Create 2 users ('leon' and 'josie')
3/. Logon on as 'josie' and create a site (apichecksite)
 - add a folder
 - upload a document (restapicheck2) into the folder
4/. Invite user 'leon' to be a member of the site 'apichecksite' as a collaborator

Using the REST API, check that both Josie and Leon can update the content of 'restapicheck2' - the document uploaded in step #3.
alfresco/api/default/public/alfresco/versions/1/nodes/{nodeid}/content?majorVersion=false

Note: I am using Postman for testing and attached the updated file to the REST API using 'body -> binary'

5/. Delete user 'josie'
6/. As user 'leon', try to 'update the content' of the document uploaded in step #3.
alfresco/api/default/public/alfresco/versions/1/nodes/{nodeid}/content?majorVersion=false
 
Observed Behaviour
 
The REST API call returns successfully to indicate the document has been updated, but when viewed thru SHARE the document has not been updated.

{
    "entry": {
        "isFile": true,
        "createdByUser": {
            "id": "josie",
            "displayName": "josie"
        },
        "modifiedAt": "2019-06-14T11:36:50.528+0000",
        "nodeType": "cm:content",
        "content": {
            "mimeType": "text/plain",
            "mimeTypeName": "Plain Text",
            "sizeInBytes": 19,
            "encoding": "ISO-8859-1"
        },
        "parentId": "60b386df-338a-457e-bbd5-0c119937a221",
        "aspectNames": [
            "rn:renditioned",
            "cm:versionable",
            "cm:titled",
            "cm:auditable",
            "cm:author",
            "cm:thumbnailModification"
        ],
        "createdAt": "2019-06-14T11:28:42.229+0000",
        "isFolder": false,
        "modifiedByUser": {
            "id": "leon",
            "displayName": "Leon Lavery"
        },
        "name": "restapicheck2.txt",
        "id": "7dd2fbc4-12f2-4b01-b9cd-cce5dac96373",
        "properties": {
            "cm:versionLabel": "1.4",
            "cm:lastThumbnailModification": [
                "pdf:1560511838121",
                "doclib:1560511838139"
            ],
            "cm:versionType": "MINOR"

 
Expected Behaviour
 
After a user has been deleted, it should still be possible to 'update the content' of a document created by the deleted user.
 
NOTE: The same problem was seen with the /nodes/{nodeid}/lock and /nodes/{nodeid}/unlock REST API's which were fixed in JIRA MNT-20481 and released as ACS v5.2.4.3