bgpd: display ingress packet queue size

bgpd: display ingress packet queue size

In the past, we always displayed the number of buffered ingress packets
as zero because there was no packet buffering in the input path and
therefore never any queue size to report. They're buffered now so we can
display something meaningful instead of 0.

Also change the inq / outq lookups to be atomic, since they can be
modified elsewhere. These should still compile down to an unfenced word
read but it's good to be explicit.

Signed-off-by: Quentin Young <qlyoung@cumulusnetworks.com>