[#250] service/policer: Don't shrink node list at unknown error

Every unknown error must not decrease shortage counter and must not
exclude faulty node from the node list, because this list will be used
later for replication.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/services/policer/check.go

@@ -85,6 +85,8 @@ func (p *Policer) processNodes(ctx context.Context, addr *object.Address, nodes
 					log.Error("could not receive object header",
 						zap.String("error", err.Error()),
 					)
+
+					continue
 				}
 			} else {
 				shortage--