Fix teuthology installations on physical Centos machines. Yum installs of packages specify a pacakge number.  Initial install of yum source changed to not fail if already done. Added yum cleans where necessary.
Fix teuthology installations on physical Centos machines.
Yum installs of packages specify a pacakge number.  Initial
install of yum source changed to not fail if already done.
Added yum cleans where necessary.

Fixes: #4768
Signed-off-by: Warren Usui <021fe6d8989d7bdb08c8700d8c426ea80a140097@inktank.com>

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