bgpd: Limit peer output queue length like input queue length

bgpd: Limit peer output queue length like input queue length

Consider this scenario:

Lots of peers with a bunch of route information that is changing
fast.  One of the peers happens to be really slow for whatever
reason.  The way the output queue is filled is that bgpd puts
64 packets at a time and then reschedules itself to send more
in the future.  Now suppose that peer has hit it's input Queue
limit and is slow.  As such bgp will continue to add data to
the output Queue, irrelevant if the other side is receiving
this data.

Let's limit the Output Queue to the same limit as the Input
Queue.  This should prevent bgp eating up large amounts of
memory as stream data when under severe network trauma.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>