iters: Report total migration time at the end
iters: Report total migration time at the end

It's useful to know what portion of total migration time
tasks were frozen.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

xemul/p.haul,arthurlockman/p.haul,avagin/p.haul,xemul/p.haul,jne100/p.haul,marcosnils/p.haul,xemul/p.haul,jne100/p.haul,marcosnils/p.haul,biddyweb/phaul,aburluka/p.haul,arthurlockman/p.haul,arthurlockman/p.haul,jne100/p.haul,arthurlockman/p.haul,aburluka/p.haul,aburluka/p.haul,avagin/p.haul,marcosnils/p.haul,avagin/p.haul,biddyweb/phaul,aburluka/p.haul,jne100/p.haul,biddyweb/phaul,xemul/p.haul,jne100/p.haul,xemul/p.haul,arthurlockman/p.haul,aburluka/p.haul