Merge pull request #246 from kriswuollett/no_fin_on_closed_stream

Stopped sending final empty frame on stream initiated in sender half-closed state.

okhttp/src/main/java/com/squareup/okhttp/internal/spdy/SpdyStream.java

@@ -670,7 +670,9 @@ public final class SpdyStream {
         }
         closed = true;
       }
-      writeFrame(true);
+      if (!out.finished) {
+        writeFrame(true);
+      }
       connection.flush();
       cancelStreamIfNecessary();
     }