FindSearchProvider doesn't get ServiceUrl and defaultIndex from app settings after a new deployment

Description

Steps to reproduce

1) Deploy a Commerce site using FindSearchProvider to Azure.
2) Make sure everything works as expected, i.e: you can search the catalog in Catalog Entry Search of Commerce Manager, the FindSearchProvider gets values from app settings of web app.
3) Update serviceUrl and defaultIndex in Mediachase.Search.config to invalid values, i.e:
serviceUrl="https://es-eu-dev-api01.episerver.net/BG2y7vnuQICkEqmEOVHAK7SVcuNX4xH4" defaultIndex="dinhnguyen_20190830".
4) Re-deploy the Commerce site.
5) Make sure app settings still have serviceUrl and defaultIndex values. And these values are valid.
6) Navigate to Commerce Manager -> Catalog Management -> Catalog Entry Search.

Expected
No errors, be able to search catalog.

Actual
"401 Unauthorized" error displays. Because the FindSearchProvider doesn't get values from app settings, it still gets value from Mediachase.Search.config file. If you restart the web app, then rebuild the Index in the Administration UI, it works as expected.