nxblob only purged when server is restarted

1. install Nuxeo
2. create a File document and upload a file to it
3. check the tmp folder
4. observe an nxblob file is present
5. wait for some time, even an hour
6. observe the file is still present
7. stop Nuxeo
8. observe the file has been purged from tmp folder

Expected behavior: in production, some environments cannot be restarted on the sole purpose of cleaning the tmp folder. This should be done on-the-fly.
Note: this is due to the nxblob file being created as a JVM temporary file, thus deleted only when the JVM stops:
https://github.com/nuxeo/nuxeo/blob/master/nuxeo-core/nuxeo-core-api/src/main/java/org/nuxeo/ecm/core/api/impl/blob/AbstractBlob.java#L138
using:
https://github.com/nuxeo/nuxeo/blob/master/nuxeo-runtime/nuxeo-runtime/src/main/java/org/nuxeo/runtime/api/Framework.java#L612