ikev1 Main+XAUTH+ModeCFG+Quick except second time Mode-Config is skipped

Some clients skip re-requesting the lease using ModeCFG when
re-connecting.  For instance when they sleep (and, mean while, the
server has deleted the ISAKMP SA since DPD failed).

Note that since the final Main mode response includes INITIAL_CONTACT,
the client should initiate ModeCFG and ask for a new lease.  Some
clients don't :-(

- client establishes connection using the exchanges

  	 Main - auth=cert; sends back INITIAL_CONTACT
	 XAUTH
	 ModeCFG - assigns 192.0.2.101/32
	 Quick - ID is 0.0.0.0/0 - 192.0.2.101/32

- client deletes connection

  this leaves server with an unused lease that can be recovered

- client re-establishes connection but skips ModeCFG

  	 Main - auth=cert; sends back INITIAL_CONTACT
	 XAUTH
	 Quick - ID is 0.0.0.0/0 - 192.0.2.101/32

  since lease is still available it is recovered during Quick

  (hack is to specify leftmodecfgclient=no leftsubnet=192.0.2.101/32)
