Implement better error diagnostics for para_client.

Implement better error diagnostics for para_client.

In case the config file contains errors, the old code caused
para_client to exit without printing an error message.

We need print_errors == 0 in client_open() because this function
is also used by para_audiod which might not have a controlling
terminal. So use gengetopt's --no-handle-error option that instructs
the command line parser not to exit on errors. This wy we can use
PARA_ERROR_LOG() to log an appropriate error message.