[Bugfix] Fix inconsistent handling of cache reset (#33481)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

vllm/v1/engine/async_llm.py

@@ -741,6 +741,7 @@ class AsyncLLM(EngineClient):
         if clear_cache:
             await self.reset_prefix_cache()
             await self.reset_mm_cache()
+            await self.reset_encoder_cache()
 
     async def resume_generation(self) -> None:
         """Resume generation after :meth:`pause_generation`."""