In previous implementation all `Read` methods read single response
per-call, so buffer could be incompletely filled w/o an error. In order
to follow `io.Reader` docs we need to continue filling the buffer while
it is possible.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
In previous implementation `ObjectListReader.Read` returned `false` on
server responded with empty ID list. This could cause premature end of
reading since the protocol does not forbid intermediate empty lists.
Do not stop if ID list from response body is empty.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
