Merge of r4621, r4641: filter_finalize fixes.

Merge of r4621, r4641: filter_finalize fixes.

*) Fixed possible request hang with filter finalization.

   With r->filter_finalize set the ngx_http_finalize_connection() wasn't
   called from ngx_http_finalize_request() called with NGX_OK, resulting in
   r->main->count not being decremented, thus causing request hang in some
   rare situations.

   Patch by Yichun Zhang (agentzh).

*) Fixed segfault with filter_finalize introduced in r4621 (1.3.0).

See the following thread for more details:
http://mailman.nginx.org/pipermail/nginx-devel/2012-May/002190.html