xml_cmp() respects 'ordered-by user' for state nodes, which violates RFC 7950

[loeliger]

When returning state XML nodes to the FE, they should not be sorted.

RFC 7950 Section 7.7.7 says:

7.7.7. The "ordered-by" Statement

The "ordered-by" statement defines whether the order of entries
within a list are determined by the user or the system. The argument
is one of the strings "system" or "user". If not present, ordering
defaults to "system".

This statement is ignored if the list represents state data, RPC
output parameters, or notification content.