ManyServer should report context information for 500 errors

[MavenRain]

In resiliency test failures, the cause of which is an internal server from an underlying ledger call, a 500 is reported, but no other context is given for the reason of the 500. Debugging will typically require not only having access to the logs of the container in which the resiliency test was run, but also the Docker logs from the underlying server that failed. Debugging cycles would be greatly reduced by providing context information in the case where the server would return a 5XX error.