xc_domain.c has a few fprintfs producing information about some error
cases. These probably should be handled as debugging messages, and
this patch implements one approach to this. The affected APIs are
unaffected and continue to return the appropriate error status.
They just are no longer as chatty when doing so.

Signed-off-by: Ben Thomas (ben@virtualiron.com)

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Ben Thomas                                         Virtual Iron Software
bthomas@virtualiron.com                            Tower 1, Floor 2
978-849-1214                                       900 Chelmsford Street
                                                    Lowell, MA 01851