sk-unix: add a peer only if it's not in a list yet
sk-unix: add a peer only if it's not in a list yet

I tried to fix that by:
commit bc2ac71c1abddbe76893c0dc1f0421311786070c
Author: Andrey Vagin <74c05afa918858348d6db8037d82fa8124870113@openvz.org>
Date:   Wed Sep 12 15:16:39 2012 +0400

    sk-unix: don't add a socket in a second time

but made a mistake and now a peer would be added only if it's in a list.

Signed-off-by: Andrey Vagin <74c05afa918858348d6db8037d82fa8124870113@openvz.org>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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