schema plugin: Generate stable fingerprint
    
    If some Param defines several values for `exclude` or `include`
    attributes then API schema hash will be unstable.
    
    First, these Param's attributes are converted to frozenset
    (ipalib/parameters.py), then `ipaserver.plugins.schema` plugin
    converts `exclude` and `include` attrs to list. Set/frozenset in
    turn, is unordered collection [0]. So, the end order of values is
    undefined.
    But due to the nature of sets:
    > two sets are equal if and only if every element of each set is
    contained in the other (each is a subset of the other)
    
    the order of values can be ignored.
    
    Note: other Param's attrs with type frozenset are not affected because
    they are not processed by the schema plugin.
    
    [0]: https://docs.python.org/3/library/stdtypes.html#set-types-set-frozenset
    
    Fixes: https://pagure.io/freeipa/issue/8955
    Signed-off-by: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>