[Cherry-Pick] [BugFix] fix instability after clearing weight (#5493)

[liyonghua0910]

Motivation

当前的 event_loop_normal 有两个状态信号，model_weight_status 是一个 SharedMemory，model_weights_signal 是一个 numpy 数组。每轮循环中，这个 np 数组会先读取 shm 的值，做一次 broadcast 之后再把自身值反向写回 shm。

另一方面，api server 也会去写 shm，在收到 /update_model_weight 调用时更新 shm 的状态为 UPDATING。如果 api server 写 shm 时，worker 刚好执行到 np 数组读取 shm 之后、写回 shm之前，np 数组读的是 CLEARED 状态，就会把 shm 的 UPDATING 信号覆盖掉，导致更新权重超时。

如果在清除权重后检测 shm 值为 CLEARED 时 sleep 住的话，可以保证 np 数组在参数 offload 期间不会去读/写 shm 的值，直到下一次 api server 收到 update 信号时 worker 才解冻，这样下一次 np 数组读的就是正确的 UPDATING 信号，不会读到上一轮的 CLEARED 信号。

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[paddle-bot]

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Codecov Report

❌ Patch coverage is 9.52381% with 19 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/2.4@c5c43e3). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/rl/dynamic_weight_manager.py	12.50%	14 Missing ⚠️
fastdeploy/worker/worker_process.py	0.00%	5 Missing ⚠️

Additional details and impacted files

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##             release/2.4    #5487   +/-   ##
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