caucase.http_wsgibase: Use less surprising attribute access pattern.

Silences a pylint warning.

caucase/http_wsgibase.py

@@ -55,7 +55,7 @@ class ChunkedFile(ProxyFile):
     result = b''
     if not self._at_eof:
       readline = self.readline
-      read = self.__getattr__('read')
+      read = self._actual_file.read
       while True:
         if self._chunk_remaining_length:
           chunk_length = self._chunk_remaining_length