xl: xl -N create -d sends json output to stdout, not stderr

xl: xl -N create -d sends json output to stdout, not stderr

                            domain config output goes to
                              before       after

  xl    create                nowhere      nowhere
  xl    create -d             stderr       stderr

  xl -N create                stdout       stdout
  xl -N create -d             stderr       stdout

It is not sensible that adding -d would cause different output on
stdout.  And that -N would produce less debug output is hardly
surprising in general and not really a problem in this case.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
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v2: New patch in this version of the mini-series.