[HiCacheStorage] fix abort request host memory leaks (#9874)

Co-authored-by: Zhiqiang Xie <xiezhq@stanford.edu>

python/sglang/srt/managers/scheduler.py

@@ -2403,6 +2403,9 @@ class Scheduler(
             # This only works for requests that have not started anything.
             # We still need to send something back to TokenizerManager to clean up the state.
             req = self.waiting_queue.pop(i)
+            if self.enable_hicache_storage:
+                # to release prefetch events associated with the request
+                self.tree_cache.release_aborted_request(req.rid)
             self.send_to_tokenizer.send_pyobj(AbortReq(req.rid))
             # For disaggregation decode mode, the request in the waiting queue has KV cache allocated.
             if self.disaggregation_mode == DisaggregationMode.DECODE: