Cloning requirements repository before pip install
Cloning requirements repository before pip install

The commit 05aa3846a0402edc9cc49f4ba36f09592004b273 into devstack exposed a bug
where pip_install is called before the requirements repository is cloned. This
change ensures that the requirements repository exists before pip_install is
called.

Change-Id: I60b157fc98691764a69cf022852e7a95fc50cdd7
Closes-Bug: #1486304

prithivm/branch01,olivierlemasle/devstack,dirkmueller/devstack,samgoon/devstack,noironetworks/devstack,parul24/devstack,Mahito/devstack,pacinete/devstack,avvocatodemarchis/devstack,dtroyer/devstack,richliu/devstack,TwinkleChawla/devstack,prithivm/branch01,dirkmueller/devstack,nawawi/openstack,pombredanne/devstack,mc2014/devstack,mc2014/devstack,openstack-dev/devstack,varunarya10/devstack,openstack-dev/devstack,costingalan/devstack,atulpatil301/devstack,group-policy/devstack,bigswitch/devstack,vsham20/devstack,pczerkas/devstack,pacinete/devstack,eharney/devstack,bswartz/devstack,thomasem/devstack,bigswitch/devstack,richliu/devstack,atulpatil301/devstack,olivierlemasle/devstack,mssumanth/devstack,pombredanne/devstack,ozamiatin/devstack,costingalan/devstack,varunarya10/devstack,samgoon/devstack,group-policy/devstack,vsham20/devstack,TwinkleChawla/devstack,mssumanth/devstack,bswartz/devstack,Mahito/devstack,thomasem/devstack,dtroyer/devstack,eharney/devstack,pczerkas/devstack,nawawi/openstack,parul24/devstack,ozamiatin/devstack,avvocatodemarchis/devstack,noironetworks/devstack