fix: grafana pvc config not working

[karl-chanel]

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[karl-chanel]

grafana在配置使用pvc时，例如设置为1G的存储时，并不会生效使用PVC，而是使用emptydir,这个问题在prometheus和loki上没有，这个问题很久就存在了，我改了几个地方就可以了