idp: when adding an IdP allow to override IdP options
    
    Use of 'ipa idp-add --provider' was supposed to allow override scope and
    other IdP options. The defaults are provided by the IdP template and
    were actually not overridden. Fix this.
    
    Fixes: https://pagure.io/freeipa/issue/9421
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>