add python-mock to testonly package list
add python-mock to testonly package list

Python-mock is needed by most of OpenStack for testability. Add
this is a testonly package. This should fix current issues with
functional tests in OpenStack that use devstack, but not tox to
run their tests.

Closes-Bug: #1341507

Change-Id: I26cbe42ace75554bae993a6d849c3b4ac649c78e

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