Views Architecture
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Vies are used to group interfaces into loginal interfaces.
When using views the sub/real interfaces handle flows only, hosts are allocated in the view interface only.

There is a SPSC queue for each sub/real interface belonging to the view interface.

NetworkInterface::viewEnqueue enqueues flows, from Flow::housekeep (incUses is used to make sure flows are not purged when still in use)
ViewInterface::viewDequeue dequeues flows in the view interface

viewed_flows_walker takes care of hosts allocation/update with the flow information coming from the sub/real interfaces.

Note: 
- in the real interface there is no host allocation, as a consequence of this the Flow contructor allocates IpAddress (cli_ip_addr) instead of Host (cli_host) 
- hosts are "Shared" between sub/real interfaces (pay attention to concurrent access)