Args/Kwargs and call RPC

If args/kwargs are defined in the config that generates the sockets in the ``RouterServer``, it causes the following issues when calling a RPC (on the RouterClient side) with args/kwargs:

- If args is already define, it throws an error saying "Multiple values for "

Normally we could just pass it nothing and it should default to the args/kwargs that was defined in the original config.

However, with the new schema stuff. The frontend will now try to validate any calls made to the zmq server. It does this by viewing the ``params_schema`` (json schema of arguments it takes). If we don't pass it an argument it will throw an error (it doesn't know that a default was defined in the RouterServer already).

The fix should be to update json schema and show that an argument/kwarg has a default value as defined by the config used by the RouterServer