Move git stuff to fetch_teuthology_branch()
Move git stuff to fetch_teuthology_branch()

michaelsevilla/teuthology,dreamhost/teuthology,michaelsevilla/teuthology,SUSE/teuthology,ktdreyer/teuthology,tchaikov/teuthology,zhouyuan/teuthology,robbat2/teuthology,ceph/teuthology,dmick/teuthology,dmick/teuthology,dmick/teuthology,zhouyuan/teuthology,ivotron/teuthology,t-miyamae/teuthology,dreamhost/teuthology,yghannam/teuthology,SUSE/teuthology,caibo2014/teuthology,SUSE/teuthology,ceph/teuthology,ivotron/teuthology,yghannam/teuthology,caibo2014/teuthology,robbat2/teuthology,tchaikov/teuthology,ktdreyer/teuthology,t-miyamae/teuthology