In PySparkling, ensure external backend can run without h2o client on spark driver side.
The goal of this change is to ensure:
-> No H2O on Spark Driver
-> Don’t need extended H2O JAR in case of PySparkling on external backend
-> The conversion from DataFrame to H2OFrame and back needs to go without running H2O
→ Implement proxy to flow UI on one of the worker nodes → leader node