ipasam: free trusted domain context on failure
    
    The context is hanging off a talloc memory context passed into the
    function so it will eventually be freed. It is better, though, to free
    it immediately when we exit from the fill_pdb_trusted_domain() function.
    
    Related: https://pagure.io/freeipa/issue/8576
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>