Fix exit_trap() error if no child processes
Fix exit_trap() error if no child processes

Bug-Id: 1285776
Change-Id: Iad7a9f2c03cc39159beda55345f232cefed10520

affo/devstack,virtualopensystems/devstack,bigswitch/devstack,kplus/devstack-moonshot,richliu/devstack,srics/devstack,atulpatil301/devstack,costingalan/devstack,vsham20/devstack,andrewrothstein/devstack,bswartz/devstack,avvocatodemarchis/devstack,bq-xiao/devstack,CloudServer/devstack,mc2014/devstack,bswartz/devstack,kplus/devstack-moonshot,pacinete/devstack,Juniper/devstack,TwinkleChawla/devstack,LoHChina/devstack,vsham20/devstack,dtroyer/devstack,varunarya10/devstack,pombredanne/devstack,varunarya10/devstack,tianweizhang/devstack,CloudServer/devstack,thomasem/devstack,neerja28/Devstack_GlusterFS,sc68cal/devstack,sc68cal/devstack,samgoon/devstack,openstack-dev/devstack,mc2014/devstack,j4/devstack,atulpatil301/devstack,JioCloud/devstack,neerja28/Devstack_GlusterFS,wenhuizhang/devstack,vishnugonela/devstack,rushiagr/devstack,pczerkas/devstack,bljgaurav/openstack-test,innodee/openstackk,HPCHub/devstack,herrsechs/devstack,Mahito/devstack,andrewrothstein/devstack,olivierlemasle/devstack,ozamiatin/devstack,pczerkas/devstack,j4/devstack,bq-xiao/devstack,bigswitch/devstack,noironetworks/devstack,group-policy/devstack,dirkmueller/devstack,parul24/devstack,sequenceiq/devstack,eharney/devstack,TwinkleChawla/devstack,BSJAIN92/OpenStack,mssumanth/devstack,samgoon/devstack,richliu/devstack,pacinete/devstack,mmasaki/devstack,eshnil2000/devstack,pombredanne/devstack,nuxeh/devstack,promptworks/devstack,ozamiatin/devstack,dirkmueller/devstack,vishnugonela/devstack,nuxeh/devstack,avvocatodemarchis/devstack,flavio-fernandes/devstack,LoHChina/devstack,mmasaki/devstack,HPCHub/devstack,BSJAIN92/OpenStack,Mahito/devstack,jamielennox/devstack,NaokiMiyata/devstack,affo/devstack,liuquansheng47/devstack,flavio-fernandes/devstack,dtroyer/devstack,noironetworks/devstack,liuquansheng47/devstack,group-policy/devstack,nawawi/openstack,promptworks/devstack,thomasem/devstack,tianweizhang/devstack,rushiagr/devstack,NaokiMiyata/devstack,openstack-dev/devstack,parul24/devstack,costingalan/devstack,bljgaurav/openstack-test,nawawi/openstack,williamthegrey/devstack,mssumanth/devstack,prithivm/branch01,herrsechs/devstack,wenhuizhang/devstack,sequenceiq/devstack,prithivm/branch01,upadhyay-prashant/devstack,upadhyay-prashant/devstack,eharney/devstack,olivierlemasle/devstack