Bugfix: Only allow rank==0 to clean up old checkpoints (#2558)

kmn1024

2025-06-25 443bc09c11f3cf89ffc573aab2021f0c933aa5b3

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BAC009S0764W0121 <|Speech|>
BAC009S0916W0489 <|Speech|>
asr_example_cn_en <|Speech|>
ID0012W0014 <|Speech|>