Makes run_tests.sh exit code match the nosetests exit value.
Makes run_tests.sh exit code match the nosetests exit value.

This will simply make the script exit with the same exit value
given by the run_tests function, addressing bug #1185755.

Change-Id: Iac1a37169db4e29d845c77d87a2df1fa07b201e1
Fixes: bug #1185755

adkerr/tempest,vedujoshi/os_tempest,cloudbase/lis-tempest,zsoltdudas/lis-tempest,itskewpie/tempest,cisco-openstack/tempest,alinbalutoiu/tempest,afaheem88/tempest_neutron,Tesora/tesora-tempest,openstack/tempest,yamt/tempest,citrix-openstack-build/tempest,akash1808/tempest,ebagdasa/tempest,flyingfish007/tempest,JioCloud/tempest,sebrandon1/tempest,hayderimran7/tempest,vmahuli/tempest,bigswitch/tempest,dkalashnik/tempest,jaspreetw/tempest,dkalashnik/tempest,hpcloud-mon/tempest,varunarya10/tempest,rzarzynski/tempest,zsoltdudas/lis-tempest,vedujoshi/tempest,pandeyop/tempest,rakeshmi/tempest,redhat-cip/tempest,pczerkas/tempest,CiscoSystems/tempest,neerja28/Tempest,jamielennox/tempest,eggmaster/tempest,Lilywei123/tempest,FujitsuEnablingSoftwareTechnologyGmbH/tempest,alinbalutoiu/tempest,manasi24/jiocloud-tempest-qatempest,Vaidyanath/tempest,afaheem88/tempest,danielmellado/tempest,manasi24/tempest,Juniper/tempest,Juraci/tempest,BeenzSyed/tempest,flyingfish007/tempest,danielmellado/tempest,eggmaster/tempest,vmahuli/tempest,cisco-openstack/tempest,sebrandon1/tempest,roopali8/tempest,nunogt/tempest,ntymtsiv/tempest,ntymtsiv/tempest,xbezdick/tempest,redhat-cip/tempest,BeenzSyed/tempest,afaheem88/tempest_neutron,tonyli71/tempest,vedujoshi/tempest,Vaidyanath/tempest,akash1808/tempest,Juraci/tempest,rzarzynski/tempest,queria/my-tempest,nunogt/tempest,izadorozhna/tempest,tudorvio/tempest,citrix-openstack/build-tempest,openstack/tempest,Mirantis/tempest,masayukig/tempest,manasi24/tempest,Tesora/tesora-tempest,pczerkas/tempest,armando-migliaccio/tempest,FujitsuEnablingSoftwareTechnologyGmbH/tempest,jaspreetw/tempest,Juniper/tempest,LIS/lis-tempest,adkerr/tempest,CiscoSystems/tempest,jamielennox/tempest,NexusIS/tempest,masayukig/tempest,itskewpie/tempest,pandeyop/tempest,hpcloud-mon/tempest,varunarya10/tempest,queria/my-tempest,roopali8/tempest,citrix-openstack-build/tempest,manasi24/jiocloud-tempest-qatempest,xbezdick/tempest,bigswitch/tempest,cloudbase/lis-tempest,Mirantis/tempest,ebagdasa/tempest,hayderimran7/tempest,Lilywei123/tempest,citrix-openstack/build-tempest,izadorozhna/tempest,tudorvio/tempest,vedujoshi/os_tempest,JioCloud/tempest,neerja28/Tempest,rakeshmi/tempest,LIS/lis-tempest,tonyli71/tempest,yamt/tempest,afaheem88/tempest,NexusIS/tempest,armando-migliaccio/tempest