BUG: Fixed BUG #4823. The issue arose because of multithreading. When testing with python was enabled, we have an interpretor initialized in a separate thread. This requires that we use correct locking mechaism for python to work correctly. Fixed that.
Currently, in the python shell, there is no way to access the connection that the client is currently connected to. Added default initialization so that paraview.ActiveConnection will point to the same connection that the client is currently connected to when the python
shell is opened.