assist #10565: close some raw file store leaks (rebased)

Progress on http://trac.openmicroscopy.org.uk/ome/ticket/10565 dealing with failures to `close()` the raw file store stateful service. Does not break http://ci.openmicroscopy.org/view/Failing/job/OMERO-5.1-merge-integration-python/lastSuccessfulBuild/testReport/junit/test.gatewaytest/test_annotation/testFileAnnotation/
--rebased-from #2001
--rebased-from #2006