Check and allocate free qdisc queue id for ports with qos parameters

Check and allocate free qdisc queue id for ports with qos parameters

ovn-northd processes the list of Port_Bindings and hashes the list of
queues per chassis. When it finds a port with qos_parameters and without
a queue_id, it allocates a free queue for the chassis that this port belongs.
The queue_id information is stored in the options field of Port_binding table.
Adds an action set_queue to the ingress table 0 of the logical flows
which will be translated to openflow set_queue by ovn-controller

ovn-controller opens the netdev corresponding to the tunnel interface's
status:tunnel_egress_iface value and configures a HTB qdisc on it. Then for
each SB port_binding that has queue_id set, it allocates a queue with the
qos_parameters of that port. It also frees up unused queues.

This patch replaces the older approach of policing

Signed-off-by: Babu Shanmugam <bschanmu@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>