Disabled python lock qcquire and release inside PyService::receive method.
There's no need to do this for the following reasons.

1. If running with SimEngine, only the main thread ever does event processing.
   So acquiring and releasing the GIL lock is un-necessary

2. If running with MiniSSF in multi-threaded MPI mode, the reader and writer threads
   are only involved in sending, receiving, packing and unpacking data, and deleting
   messages that are already sent. No python calls are made by these threads. All
   simulation functions (event processing) and thus all python call-backs are carried
   out by the main thread, and here again acquiring and releaseing GIL lock is unnecessary

3. If running with MiniSSF in non multi-threaded MPI mode (single threaded, funneled
   or serialized), the main thread (which executes the python driver script initially) and
   the read-write thread "switch" roles just before the start of the simulation
   (see universe_sched.cc::run() ), i.e the main thread becomes the rw thread and
   the newly created rw thread assumes the role of the main thread (event processing). Here
   too only one thread ever treads in Python space at any given time, so the GIL routines
   should be un-necessary.