Posting a json payload to the http-binding changes the root jcr:primaryType

If you post with curl a json payload to oak (oak-run and httpbinding) the jcr:primaryType of root changes from rep:root to nt:unstructured.

Step for reproducing

• Fire oak with oak-run org.apache.jackrabbit.oak.run.Main and parameters: server /path/to/oak-repo
• check the rep:root is fine

  curl -u admin:admin -H "Accept: application/json" http://localhost:8080
  {"jcr:primaryType":"rep:root","jcr:system":{},"rep:security":{},"oak:index":{}}
  

• post a json payload for creating /content

  curl -u admin:admin -H "Accept: application/json" -H "Content-Type: application/json" -X POST -d "{\"jcr:primaryType\":\"oak:unstructured\"}" http://localhost:8080/content
  

• check and see the "/" changing to nt:unstructured

  curl -u admin:admin -H "Accept: application/json" http://localhost:8080
  {"jcr:primaryType":"nt:unstructured","content":{},"jcr:system":{},"rep:security":{},"oak:index":{}}