Can we remove the parameter server implementation with Python

[Yancey0623]

There is two entry point of the parameter server instance, the one is Python /elasticdl/python/ps, another one is /elasticdl/go/cmd/elasticdl_ps.

It seems the Python code is useless, can we remove it from this repo? c.f. https://github.com/sql-machine-learning/elasticdl/blob/6b1a1b2cd59d07bba642ff648afc0ad42160ee16/elasticdl/python/master/master.py#L414

[QiJune]

Yes, we could remove the parameter server implementation with Python.

The parameter server implementation with Go has been used in production already. It's safe to remove Python codes.