the_metal: fix typo in buffer creation the_metal

Tested with the following example patch over a slow connection:

  --- a/examples/the_metal.rb
  +++ b/examples/the_metal.rb
  @@ -10,7 +10,7 @@ class Application
       # when write_head is called or have Transfer-Encoding: chunked
       # (in which case res.write must chunk for us)
       res.write_head 200, 'Content-Type' => 'text/plain'
  -    res.write "Hello World\n"
  +    1000000.times { res.write "Hello World\n" }
       res.finish
     end
   end

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/yahns/the_metal.rb b/lib/yahns/the_metal.rb
index 4d96bb7..0d7bb43 100644
--- a/lib/yahns/the_metal.rb
+++ b/lib/yahns/the_metal.rb
@@ -38,7 +38,7 @@ class Yahns::TheMetal # :nodoc:
           buf = rv # hope the skb grows when we loop into the trywrite
         when :wait_writable, :wait_readable
           if @wbuf
-            @wbuf = Yahns::Wbuf.new(*@obuf)
+            @wbuf = Yahns::Wbuf.new(*@wbuf)
             @last_rv = @wbuf.wbuf_write(@io, buf) # write-in-full behavior
             return
           else