pstree: fix error handling
pstree: fix error handling

pstree.c:273:3: warning: Value stored to 'ret' is never read
                ret = 0;
                ^     ~

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

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