* Only sent a flush bucket down the chain if buckets where sent down the chain

* Only sent a flush bucket down the chain if buckets where sent down the chain
  before that could still be buffered in the network filter. This is the case
  if we have sent an EOS bucket or if we actually sent buckets with
  data down the chain. In all other cases we either have not sent any
  buckets at all down the chain or we only sent meta buckets that are
  not EOS buckets down the chain. The only meta bucket that remains in
  this case is the flush bucket which would have removed all possibly
  buffered buckets in the network filter.
  If we sent a flush bucket in the case where not ANY buckets were
  sent down the chain, we break error handling which happens AFTER us.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@605314 13f79535-47bb-0310-9956-ffa450edef68