Add Cluster.write_file()
Add Cluster.write_file()

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