deduplication: make it recursively deduplicate all parent snapshots
deduplication: make it recursively deduplicate all parent snapshots

If we write a page into image and punch it from parnet, checking
only one level down is not enough -- the iovec can reside deeper.

That said, make the hole punching be recursive.

Signed-off-by: Tikhomirov Pavel <2566b75157ba49177214ae1d5f51030018b1e134@gmail.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

tych0/criu,sdgdsffdsfff/criu,tych0/criu,rentzsch/criu,AuthenticEshkinKot/criu,fbocharov/criu,LK4D4/criu,tych0/criu,eabatalov/criu,LK4D4/criu,AuthenticEshkinKot/criu,tych0/criu,efiop/criu,sdgdsffdsfff/criu,svloyso/criu,biddyweb/criu,ldu4/criu,gablg1/criu,sdgdsffdsfff/criu,svloyso/criu,sdgdsffdsfff/criu,rentzsch/criu,KKoukiou/criu-remote,ldu4/criu,rentzsch/criu,gonkulator/criu,marcosnils/criu,LK4D4/criu,wtf42/criu,eabatalov/criu,fbocharov/criu,rentzsch/criu,KKoukiou/criu-remote,wtf42/criu,eabatalov/criu,biddyweb/criu,ldu4/criu,eabatalov/criu,sdgdsffdsfff/criu,biddyweb/criu,fbocharov/criu,gonkulator/criu,KKoukiou/criu-remote,rentzsch/criu,AuthenticEshkinKot/criu,marcosnils/criu,AuthenticEshkinKot/criu,gonkulator/criu,gablg1/criu,fbocharov/criu,KKoukiou/criu-remote,gonkulator/criu,KKoukiou/criu-remote,ldu4/criu,wtf42/criu,efiop/criu,gablg1/criu,fbocharov/criu,biddyweb/criu,rentzsch/criu,efiop/criu,marcosnils/criu,gablg1/criu,eabatalov/criu,biddyweb/criu,marcosnils/criu,kawamuray/criu,svloyso/criu,svloyso/criu,gablg1/criu,kawamuray/criu,fbocharov/criu,KKoukiou/criu-remote,gablg1/criu,wtf42/criu,LK4D4/criu,tych0/criu,ldu4/criu,ldu4/criu,LK4D4/criu,svloyso/criu,efiop/criu,efiop/criu,LK4D4/criu,kawamuray/criu,AuthenticEshkinKot/criu,eabatalov/criu,sdgdsffdsfff/criu,kawamuray/criu,svloyso/criu,marcosnils/criu,wtf42/criu,biddyweb/criu,wtf42/criu,tych0/criu,gonkulator/criu,efiop/criu,AuthenticEshkinKot/criu,kawamuray/criu,marcosnils/criu,gonkulator/criu,kawamuray/criu