proc: Don't use FILE * to reach children
proc: Don't use FILE * to reach children

The same reasoning as for personality file -- switch to
plan open + read + close.

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

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