Description of problem:
SingleLogoutService from the sp-metadata.xml file is not used when browser is redirected to the idp.
PicketLink takes the value from the SingleLogoutService tag and puts it in the Destination field of the LogoutRequest, but the SingleLogoutService is not used when redirecting the browser to the IDP for the logout.
A workaround is to set the LogOutUrl configuration option in the `WEB-INF/picketlink.xml` file.
Deferring as there is a workaround