Split function create_net_objects_from_source to multiple smaller functions + create unit tests for them

• try move function from Firewall class to FirewallCisco class. First try to check if if self.class.name == 'FirewallJuniper': is called in integration tests. So add there a logger and look for it in logs in Gitlab
• If none found, then move it to FirewallCisco class. Remove if self.class.name == 'FirewallJuniper':
• split function to multiple functions - the rule is that keep first level zanorenie and move the other levels of zanorenie to separate methods
• make unit test for new functions