Make stop_swift() more robust for Grenade
Make stop_swift() more robust for Grenade

stop_swift() wasn't calling screen_stop() so the pid files and screen
sessions were not being cleaned up.  DevStack doesn't really care but
Grenade does for the 'base' copy of DevStack.  This should be backported
to stable/havana for this reason.

Change-Id: Ib5afb321cef2b7ad74e69a3fd0d1dad469f78b11

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