Display stderr logs as expected on K8s (#2696)

## Related issue number

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Fixes #2693

Signed-off-by: Tao He <linzhu.ht@alibaba-inc.com>

coordinator/gscoordinator/coordinator.py

@@ -243,6 +243,7 @@ def ConnectSession(self, request, context):
         # Session connected, fetch logs via gRPC.
         self._streaming_logs = True
         sys.stdout.drop(False)
+        sys.stderr.drop(False)
 
         return message_pb2.ConnectSessionResponse(
             session_id=self._session_id,
@@ -270,6 +271,7 @@ def CloseSession(self, request, context):
 
         # Session closed, stop streaming logs
         sys.stdout.drop(True)
+        sys.stderr.drop(True)
         self._streaming_logs = False
         return message_pb2.CloseSessionResponse()