Back out the recent change to ap_get_brigade, to make it use indirection

Back out the recent change to ap_get_brigade, to make it use indirection
again.  The problem is that the amount of data read from the network,
is not necessarily the amount of data returned from the filters.  It is
possible for input filters to add bytes to the data read from the network.

To fix the original bug, I just removed the line from ap_get_client_block
that decremented r->remaining, we allow the http_filter to do that for
us.

I have also removed an incorrect comment.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89041 13f79535-47bb-0310-9956-ffa450edef68