Bug when stopping `RemoteKerConnection`

[bnouwt]

In RemoteKerConnection.stop(...) there is a bug where the RemoteKerConnection should provide its own URL, but it provides the Knowledge Directory URL.

[bnouwt]

Also, the REST API operation used in this method (DELETE /runtimedetails/{ker_id}) is meant to notify other KERs that this KER is stopping, however, it is used when stopping another KER. This last call should not happen.

Note that when we remove this last call, the RemoteKerConnection.stop(...) method is used nowhere, because we did not implement any mechanism when a Knowledge Engine Runtime is stopping. Most of the time we just kill -9 the process.