Descriptions of the get addr and port in socket.h need to be updated

Currently there are a list of failing error conditions for the following methods:

```
virtual socket_error_t getLocalAddr(SocketAddr *addr) const;
virtual socket_error_t getRemoteAddr(SocketAddr *addr) const;
virtual socket_error_t getLocalPort(uint16_t *port) const;
virtual socket_error_t getRemotePort(uint16_t *port) const;
```

Only some of these error conditions are directly returned by the socket method implementations, all others are returned by the underlying calls to the specific api functions. As they are currently not guaranteed to honour those error conditions, this documentation should be updated.

This may not be trivial however, as ideally this higher level api would have all possible error conditions without having to refer to the api implementation documentation.