We have setup ADFS in Confluence instance .( Not able validate due to the below mentioned issue)
The DB is also updated with property com.atlassian.plugins.authentication.samlconfig.redirect-on-login set to TRUE and App was rebooted.
In the UI also settings is saved as Use SAML As Primary Authentication , this settings remains for some time( Maybe an Hour) and its getting automatically changed to Use SAML As Secondary Authentication.
( some Alert generated related to PROXY , sometime when was trying to save settings)