fix(hz): pb model_dir corner case

[FGYFFFF]

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fix

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修复 pb 场景下，指定 "model_dir=."时，导致的 import 路径有问题

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en: fix a problem in the pb scenario when specifying "model_dir=." that cause a problem with the import path
zh(optional): 修复 pb 场景下，指定 "model_dir=."时，导致的 import 路径有问题

import (
       _ "a/b/c//api"
)

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