ceph_manager: mount_osd_data expects osd as a str
ceph_manager: mount_osd_data expects osd as a str

Signed-off-by: Samuel Just <8c40222f34b9721b5d5709d4ed45337913ea1c3e@inktank.com>

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