fix wrong "create" state on the preview mode of the importer

[kpsherva]

@JakobMiesner I just did a test: I created manually https://sandbox-cds-ils.web.cern.ch/backoffice/documents/x0tap-26g10 and did again an O'Reilly import in preview to see if it matched. It did: But it shows "Create" as action, which is incorrect. It should be an update. How can I avoid that the importer created a duplicate?

@lydipi could you try again on sandbox but in import mode (not preview)? I would like to see if it is simply preview mode which shows a wrong label

Originally posted by @kpsherva in #879