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

This is a variation of dpd-03, except it uses multiple tunnels.

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

Order of Operations:

- WEST has revival impaired

  When a +UP connection fails, and revival is triggered, it gets as
  far as installing a %trap, but stops short of trying to initiate a
  new connection.

  This way, ping can be used to trigger revival.

- EAST sets up for tunnel

- WEST initiates tunnels to east

  (and connection is confirmed as established on east)

- We idle for 20 seconds proving DPD R_U_THERE/R_U_THERE_ACKs work.

  (after which trafficstatus should still show output)

- WEST blocks inbound and outbound traffic

- Both sides trigger a DPD Timeout:

  EAST tears down the state/policy

  WEST triggers revival, tearing down state, and, per above,
  installing a %trap policy

- WEST removes the traffic block

- WEST sends icmp packets to east, triggering a renegotiation of each
  aof the tunnels
