read fiber spans default values from eqpt_config.json[Spans]
=>if con_in/con_out is None or not defined in params
Rename connector_loss_in/out to con_in/out for consistency
update parser tests to accept the new con_in/out syntax and the new default
values
Signed-off-by: Jean-Luc Auge <jeanluc.auge@orange.com>