net-test: packetdrill: fix bug in remote mode packet sniffing direction

Fix wire_server_netdev_receive() to reflect the fact that in remote
mode the server is sniffing packets that are inbound (whereas in local
mode we are sniffing *outbound* packets).

This was a bug introduced in "net-test: packetdrill encap
support: refactor packet receive loops into one loop".

Remote mode has been broken since the addition of encapsulation
support, partly due to this issue.

Change-Id: Ia92f70f48ae90cb2e089ee51d728473a12c63595