This tests the RFC3706 DPD implementation, with dpdaction=hold on east,
and dpdaction=hold on west.

This means both sides with %trap the eroute awaiting a new packet to
trigger reestablishment of the tunnel.

Order of Operations:

1) East sets up for tunnel
2) West initiates tunnel to east
3) We idle for 20 seconds, to prove that DPD R_U_THERE/R_U_THERE_ACKs work.
4) West blocks traffic on eth0
5) Both sides trigger a DPD Timeout:
	East puts the eroute into %trap
	West puts the eroute into %trap
6) West removes the traffic block
7) West sends icmp packets to east, triggering a renegotiation of the tunnel