Add tests for "order none" RRset ordering rules

Add tests for "order none" RRset ordering rules

Make sure "order none" RRset ordering rules are tested in the
"rrsetorder" system test just like all other rule types are.  As the
check for the case of no "rrset-order" rule matching a given RRset also
tests "order none" (rather than "order random", as the test code may
suggest at first glance), replace the test code for that case so that it
matches other "order none" tests.