ofproto-dpif: Use send_packet() instead of netdev_send().

ofproto-dpif: Use send_packet() instead of netdev_send().

netdev_send() directly sends a packet using Linux mechanisms, skipping
our kernel module. Several upper layer abstractions are built on top of
the kernel module, so this means that we loose stats, sFlow, etc. on
these packets. This changes bonding, LACP, and STP to use send_packet()
as CFM does, which uses the standard kernel mechanisms and provides a
single place that needs to be updated.