Fix wrong input type

_safe_close methods accepts a list of fds, not a single fd.

Change-Id: I04ac8c396042b99c15328832ae70cebc2480714a

storlets/gateway/gateways/container/runtime.py

@@ -735,4 +735,4 @@ class StorletInvocationProtocol(object):
             # so we should catch an exception and suppress it here
             self.logger.exception('Unexpected error at writing input data')
         finally:
-            self._safe_close(fd)
+            self._safe_close([fd])