common: bufferlist::read_file: return read errors
common: bufferlist::read_file: return read errors

Don't ignore errors when reading a file with buffer::list.

Signed-off-by: Colin McCabe <c0eabe2887ac1e91c280795b9fca010e21066283@hq.newdream.net>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph