Some fixes for early support for Python3.10

The loop parameter has been removed from most of asyncio‘s high-level API following deprecation in Python 3.8.

gns3server/utils/asyncio/telnet_server.py

@@ -424,7 +424,7 @@ if __name__ == '__main__':
                                                                                                       stdin=asyncio.subprocess.PIPE)))
     server = AsyncioTelnetServer(reader=process.stdout, writer=process.stdin, binary=False, echo=False)
 
-    coro = asyncio.start_server(server.run, '127.0.0.1', 4444, loop=loop)
+    coro = asyncio.start_server(server.run, '127.0.0.1', 4444)
     s = loop.run_until_complete(coro)
 
     try: