Cyclic Dependency between Service API and Remote Workflow Controller

[heikomuller]

Please describe the problem.
The cyclic dependency between the flowserv.service.local.LocalAPIFactory and the flowserv.controller.remote.engine.RemoteWorkflowController makes it currently impossible to instantiate the backend (in the init_backend function) from the environment variables FLOWSERV_BACKEND_CLASS and FLOWSERV_BACKEND_MODULE.

Describe the solution you'd like
We either need to think ablut breaking this dependency or change the protocol for instantiating backends (e.g., add an additional init() call that passes the API factory object to the created backend).