[Bugfix] fix encoder cache leak of waiting requests in scheduler to solve stuck in CPU scheduling (#31857)

Signed-off-by: frelam <frelam112233@gmail.com>
Co-authored-by: Roger Wang <hey@rogerw.io>

vllm/v1/core/sched/scheduler.py

@@ -598,6 +598,11 @@ class Scheduler(SchedulerInterface):
 
                 if new_blocks is None:
                     # The request cannot be scheduled.
+
+                    # NOTE: we need to untouch the request from the encode cache
+                    # manager
+                    if request.has_encoder_inputs:
+                        self.encoder_cache_manager.free(request)
                     break
 
                 # KVTransfer: the connector uses this info to determine