release state cache (#4462)

Author: CUHKSZzxy

lmdeploy/pytorch/engine/model_agent/agent.py

@@ -1208,6 +1208,7 @@ async def sleep(self, level: int = 1):
         if self.dist_config.dp > 1:
             await self.state.to_sleep.wait()
         self.cache_engine = None
+        self.state_cache_engine = None
         self.reset_graph_runner()
         device = 'cpu' if level == 1 else 'meta'
         self.patched_model.get_model().to(device=device, non_blocking=True)
@@ -1245,4 +1246,5 @@ def release(self):
         self.reset_graph_runner()
         self.patched_model = None
         self.cache_engine = None
+        self.state_cache_engine = None
         torch.cuda.empty_cache()