RPC fibonacci python tutorial

[MisterCodeRalf]

Leaving connections open is not a good idea. This may lead to overflows:

in the rpc_client.py file in the def init(self) a close should be defined:

def close(self):
self.connection.close()

this should then be called at the end of the rpc_client.py file:

fibonacci_rpc.close()

[michaelklishin]

These are tutorials. They cannot demonstrate everything at once. I would argue that using short lived connections in tutorials is/would be a bigger issue for us because people copy code into production and create connection churn, which is so problematic it has two dedicated sections in various doc guides.