Switch ap_filter_flush() to ap_pass_brigade(). This removes a layer of

Switch ap_filter_flush() to ap_pass_brigade(). This removes a layer of
function calls, provides type safety for the ap_filter_t*, and
clarifies what is really going on (i.e. we aren't sending a FLUSH
bucket of any kind).

* mod_dav.c (dav_send_multistatus, dav_method_propfind): change the
    ap_filter_flush call to ap_pass_brigade; flip the params to match
    the prototype.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@100647 13f79535-47bb-0310-9956-ffa450edef68