solve broken partial file sends

We can't force the wsi state to HTTP_BODY without considering the callback
may already have set the state to sending a file.

This fixes the bug that we can get stalled in the test app at
"choked before able to send whole file"

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/lib/handshake.c b/lib/handshake.c
index 48b2767..69daf75 100644
--- a/lib/handshake.c
+++ b/lib/handshake.c
@@ -277,11 +277,13 @@
 							      AWAITING_TIMEOUT);
 
 				/*
+				 * (if callback didn't start sending a file)
 				 * deal with anything else as body, whether
 				 * there was a content-length or not
 				 */
 
-				wsi->state = WSI_STATE_HTTP_BODY;
+				if (wsi->state != WSI_STATE_HTTP_ISSUING_FILE)
+					wsi->state = WSI_STATE_HTTP_BODY;
 				goto http_postbody;
 			}