Fix resuming CCTcpip

[thc3si]

When an auxiliary such as InstrumentControlAuxiliary is suspended then resumed, its channel has its methods _cc_close, then _cc_open called.

The CCTcpip connector currently doesn't support that: once _cc_close has been called, _cc_open cannot be called anymore. This is because socket.socket does not support reopening a closed socket.

The changes here create the socket in _cc_open, allowing multiple _cc_open / _cc_close cycles.

Relevant test (tests/test_cc_tcp_ip.py) has been updated, because it depended on using various methods of CCTcpip without first calling _cc_open. This use case should not happen in the real world, and doesn't work anymore now that the socket is only created in _cc_open.