added (passing) tests for using parallel subrequests after ngx.eof().
added (passing) tests for using parallel subrequests after ngx.eof().

yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx,yeahdongcn/SEnginx