install test-reqs when TESTONLY packages are installed
install test-reqs when TESTONLY packages are installed

INSTALL_TESTONLY_PACKAGES in devstack only impacts .deb/.rpm files
even though most of our test requirements are actually specified
in python. This will do an explicit install of test-requirements.txt
if pip_install is called with args that look like a directory,
and test-requirements.txt exists in that directory.

Change-Id: Id21e282ddc945c819c9c8c4d724658e28bfde785

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