NXRM to NXRM Nuget v3 proxying still results in direct requests to nuget.org

Proxying a nuget v3 repo from one Nexus instance to another, still results in the proxying instance making direct calls to *.nuget.org. 

To reproduce:

1. On Nexus instance A, configure Nuget v3 proxy to https://api.nuget.org/v3/index.json 
2. On. Nexus instance B, configure Nuget v3 proxy to instance A e.g. http://localhost:8082/repository/nuget-v3-proxy/index.json
3. Enable DEBUG logging on org.apache.http on instance B.
4. Perform a nuget install with instance B as the source.
5. Observe nexus.log.

Expected:

Remote v3 requests from instance B should be made to Nexus instance A.

Actual:

Only the initial request for the index.json is made to instance A. Remaining requests are being made directly to *.nuget.org.