Accessing obj_request->img_request union field is only valid for object
requests associated with an image (i.e. if obj_request_img_data_test()
returns true).  rbd_osd_req_format_read() used to do more, but now it
just sets osd_req->snap_id.  Standalone and stat object requests always
go to the HEAD revision and are fine with CEPH_NOSNAP set by libceph,
so get around the invalid union field use by simply not calling
rbd_osd_req_format_read() in those places.
Reported-by: NDavid Disseldorp <ddiss@suse.de>
Signed-off-by: NIlya Dryomov <idryomov@gmail.com>
Reviewed-by: NAlex Elder <elder@linaro.org>
Reviewed-by: NDavid Disseldorp <ddiss@suse.de>