Joining additional machines to an ArcGIS GIS Server 10.5 site that is upgraded from an earlier version fails with the following error, "Unable to access directory path '/relational-datastore-types' on the shared config-store."

Description

After upgrading to ArcGIS GIS Server 10.5, joining additional machines to an ArcGIS Server site (single or multi-node) using a network path for the configuration store fails with the following error: 

Error:   
Unable to access directory path '/relational-datastore-types' on the shared config-store.

This issue occurs in the following cases:

• After an upgrade, joining a site or adding a machine to a site using a newly installed ArcGIS 10.5 machine
• After an upgrade, joining a site or adding a machine to a site using an ArcGIS Server machine upgraded to ArcGIS 10.5

This issue does not occur in the following cases:

• Upgrading single or multi-node sites (all operations, except Add/Join, work as expected.)
• Upgrading a single machine site with a local path to the config-store, editing the config-store path to a network path, and following the Add machine and Join site workflows
• All upgrades from earlier versions (not including ArcGIS 10.5) to ArcGIS 10.5.1 or newer (single, multi-node, or local/shared path)

Cause

The host ArcGIS Server site is upgraded to ArcGIS 10.5 from an earlier version. ArcGIS Server searches for a path to the /relational-datastore-types folder, which is unintentionally added to the configuration store path in ArcGIS Server 10.5. This folder is not in the configuration store root path for newer versions.

Note:
This issue does not occur when upgrading from an earlier version to ArcGIS Server 10.5.1 or newer.

Workaround

1. Create a new folder at the folder path below in the ArcGIS Server configuration store folders.

   ...\arcgisserver\config-store\'relational-datastore-types

2. Grant permissions to this folder for the ArcGIS Server service account (domain account).
3. Rejoin the site.

Note:   
It is recommended to delete the relational-datastore-types folder before upgrading to ArcGIS Server 10.5.1 or later from ArcGIS for Server 10.5 to ensure there is no extra folder left in ArcGIS 10.5.1 or later releases. 

Steps to Reproduce