The nsmode.xml file does have the following namespace declaration attribute on 
the <z:a> element: xmlns:p="http://www.example.com/p2.uri"

The expected output for constr-cont-nsmode-1 (both constr-cont-nsmode-1.xml and 
constr-cont-nsmode-1b.xml) doesn't expect this namespace declaration attribute.
As the query prolog specifies "declare copy-namespaces preserve, inherit;" we 
believe the expected output should include that specific namespace declaration 
attribute.
See http://www.w3.org/TR/xquery/#id-content,  1.e.ii.D.I and 1.e.ii.D.II

I.e. we expect output as follows:
<p xmlns:p="http://www.example.com/p.uri"><z:a 
xmlns:p="http://www.example.com/p2.uri" 
xmlns:z="http://www.example.com/z.uri"><b 
xmlns:y="http://www.example.com/y.uri" 
xmlns:z="http://www.example.com/z2.uri"/></z:a></p>