Slice filter: clear original Accept-Ranges. The slice filter allows ranges for the response by setting the r->allow_ranges flag, which enables the range filter. If the range was not requested, the range filter adds an Accept-Ranges header to the response to signal the support for ranges. Previously, if an Accept-Ranges header was already present in the first slice response, client received two copies of this header. Now, the slice filter removes the Accept-Ranges header from the response prior to setting the r->allow_ranges flag.