bgpd: With io limit allow parsing to continue even if memory is low

bgpd: With io limit allow parsing to continue even if memory is low

Commit: a0b937de428e14e869b8541f0b7810113d619c2e

Introduced the idea of a input Q packet limit.  Say you read in
635000 bytes of data and the input Q is already at it's limit
(currently 1000) then when bgp_process_reads runs it will
assert because there is less then a BGP_MAX_PACKET_SIZE in ibuf_work.

Don't assert as that it's irrelevant.  Even if we can't read a full packet
in let's let the whole system keep working as that as the input Q length
comes down we will start pulling down the ibuf_work and it will be ok.

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