You are not able to find the OAUTH tokens in the table "oauth_credential" under the field 'Token'
This is an expected behaviour from Madrid release. Its related to the security constraints not to expose the token publicly which may lead to misuse of the token generated.
You can find a new field named "Token received" in the same table which is two way encrypted. There is no other change in the functionality.
You can check the field named "Token received" in the table "oauth_credential" to find the token. Its two way encrypted and can be decryoted using the method "encr.decrypt();"