debugnet: Fix false-positive assertions for dp_state
debugnet_handle_arp:
An assertion is present to ensure the pcb is only modified when the state is DN_STATE_INIT. Because debugnet_arp_gw() is asynchronous it is possible for ARP replies to come in after the gateway address is known and the state already changed.
debugnet_handle_ip:
Similarly it is possible for packets to come in, from the expected server, during the gateway mac discovery phase. This can happen from testing disconnects / reconnects in quick succession. This later causes some acks to be sent back but hit an assertion because the state is wrong.
Reviewed by: cem, debugnet_handle_arp: markj, vangyzen
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D31327