SPDY: fix connection leak

 * If ngx_http_spdy_finalize_connection() was called,
   ngx_http_spdy_body_filter(r, in) should return NGX_ERROR.
 * The write timer of spdy connection may be deleted.
Merge pull request #527 from chobits/spdy_bugfix

SPDY: fix connection leak
Merge pull request #526 from chobits/master

dynamic_resolve.t: skip cases without Net::DNS::Nameserver
Update test-nginx library to official git commit 8d5c866836

 Official source tree:
   https://github.com/openresty/test-nginx/tree/8d5c8668364251cdae01ccf1ef933d80b642982d