Mxnet-model-server

Allows custom HTTP status in mms.service.Service to be returned to client

This release contains minor fixes to bump up Netty & Log4j versions.

This release contains minor fixes to make sure resource cleaning is done for terminated worker threads
* Terminates the STDOUT and STDERR ReaderThreads for a Worker when it is scaled down

This release contains API changes and fixes to make sure resource cleaning is handled synchronously.
* Load model API sends a conflict response instead of a bad request response when trying to register an already registered model. 851
* Unregister model API is now synchronous and will wait until all resources are cleaned before sending a response back. A timeout feature was also added to config if users don't want to wait. 853

This release contains a minor bug fix for Python 2 support.
* Changed the python protocol handler between frontend and backend to support python 2 better.