LDAP: Return the error message from the extended operation password change also on failure
    
    Resolves: https://pagure.io/SSSD/sssd/issue/4015
    
    If password change fails, the tevent request would call
    TEVENT_REQ_RETURN_ON_ERROR before returning the error message that comes
    from the server, so the server message would not be propagated to the caller.
    
    This regressed in cf1d7ff
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>