ceph: add default btrfs mkfs options
ceph: add default btrfs mkfs options

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