pstree: Drop redundant nil test in prepare_pstree
pstree: Drop redundant nil test in prepare_pstree

This as well releases pb entry on error path, not
a big deal since we're exiting in case of error
but still.

Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@openvz.org>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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