phaul: Handle network-(un)lock notifies from CRIU

These will be called to respectively block and unblock networking
for container.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
htypes: Distinguish htypes initialization on source and destination

Some differences in behavior appear on both sides, prepare for that.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
ovz: Load CT config on source node before dumping

We'll need to lock networking for CT, for that we need to
knon the network devices of it. The devices info is available
from the config file.

Fortunatelly the cfg parsing is already written, so just move
this code.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
ovz: Properly lock and unlock networking

Lock network means downing all the veths, unlocking -- upping them.

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