Fix the final boundary in resumable multipart media uploads.

Reviewed in http://codereview.appspot.com/5450107/.
diff --git a/tests/test_http.py b/tests/test_http.py
index f502bac..b7054dc 100644
--- a/tests/test_http.py
+++ b/tests/test_http.py
@@ -109,7 +109,7 @@
     self.assertEquals(new_req.body, '{}')
     self.assertEquals(new_req.http, http)
     self.assertEquals(new_req.resumable.to_json(), media_upload.to_json())
-    self.assertEquals(new_req.multipart_boundary, '---flubber')
+    self.assertEquals(new_req.multipart_boundary, '---flubber--')
 
 EXPECTED = """POST /someapi/v1/collection/?foo=bar HTTP/1.1
 Content-Type: application/json