fallback call to ceph for versions < dumpling

Signed-off-by: Alfredo Deza <alfredo@deza.pe>

check for errno.EACCES directly instead of parsing output

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
simpler try except for check_call with no std capturing

Signed-off-by: Alfredo Deza <alfredo@deza.pe>