fix(ml): race condition when loading models (#3207)

* sync model loading, disabled model ttl by default

* disable revalidation if model unloading disabled

* moved lock

machine-learning/app/config.py

@@ -13,7 +13,7 @@ class Settings(BaseSettings):
     facial_recognition_model: str = "buffalo_l"
     min_tag_score: float = 0.9
     eager_startup: bool = True
-    model_ttl: int = 300
+    model_ttl: int = 0
     host: str = "0.0.0.0"
     port: int = 3003
     workers: int = 1