SAML SLO sends back-channel call even front-channel is enabled

[rksk]

When we have selected a front-channel SAML logout method, the SAML logout request is going in the front-channel as expected for both POST and Redirect bindings. But it tries to send the back-channel request always despite the Logout method.

Steps to reproduce

• Enable debug logs for org.wso2.carbon.identity.sso.saml
• Configure a SAML sp with followings

  SLO Request URL = "http://pqr.local" Logout Method = "Front-Channel Logout POST/Redirect" Enable IdP Initiated SLO = true

• Try to do IdP initiated SAML SLO.

  https://localhost:9443/samlsso?slo=true&spEntityID=saml2-web-app-pickup-manager.com

• Following log is written

  DEBUG {org.wso2.carbon.identity.sso.saml.logout.LogoutRequestSender} - Error while executing http request. java.net.UnknownHostException: pqr.local: Name or service not known at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)

[malithie]

This was not observed in SP-initiated SLO flow