Fix ONEE during in-place import. (fix #12498)

This PR fixes https://trac.openmicroscopy.org.uk/ome/ticket/12498. The new field allows for persisting the object value throughout method calls. `rawFileStore` is first closed in the `checkLocation` method but it wasn't set to `null`, so the check in `cleanupUpload` always passed and we were trying to call `close()` twice. With this PR the value of `omero.import.active_close` decides where the raw file store object will be closed.

To test: try out different combinations of in-place import (both with `omero.import.active_close` set to `true` and `false` - use `JAVA_OPTS` to set it; see note in http://www.openmicroscopy.org/site/support/omero5/sysadmins/in-place-import.html#limitations).

This PR most probably won't get rebased. It still raises a question if we need `omero.import.active_close` on `develop` in the first place.