Only initialize the SAML IDP when actually enabled
    
    This has the same reasoning as the OpenID patch (commit
    ac7c20cca81c3d23ee66f224030b316bdff2274a), with additionally
    that it will otherwise error on finding the metadata.
    (This is not critical though as it will retry loading and
    succeed, this is just to make it not spit that error).
    
    Signed-off-by: Patrick Uiterwijk <puiterwijk@redhat.com>
    Reviewed-by: Rob Crittenden <rcritten@redhat.com>