Fix the code that processes the PIX query to correctly look up the fullUrl

[wluyima]

When one submits a PIX query i.e. like the one below,
https://localhost:3000/fhir/Patient/$ihe-pix?sourceIdentifier=system|patientId

The returned payload is missing the valueReference field i.e. the fullUrl of the patient, this is because the responsible code looks up the fullUrl on the resource field instead of the entry field from the hapi fhir response as seen here.

Can this be fixed please? I can apply the fix and issue a PR if you guys are busy