fix http_post & http_simple redirect

shadowsocks/obfsplugin/http_simple.py

@@ -175,9 +175,7 @@ class http_simple(plain.plain):
             if len(ret_buf) >= 7:
                 self.has_recv_header = True
                 return (ret_buf, True, False)
-            if len(ret_buf) == 0:
-                return self.not_match_return(buf)
-            return (b'', True, False)
+            return self.not_match_return(buf)
         else:
             return (b'', True, False)
 
@@ -244,9 +242,7 @@ class http_post(http_simple):
             if len(ret_buf) >= 7:
                 self.has_recv_header = True
                 return (ret_buf, True, False)
-            if len(ret_buf) == 0:
-                return self.not_match_return(buf)
-            return (b'', True, False)
+            return self.not_match_return(buf)
         else:
             return (b'', True, False)