Fix fuse tests.
Fix fuse tests.

Normally, since the mount is a separate process from Girder, the Girder
process can stop and free resources before unmount is performed.  In
tests, the Girder process stays running via the test infrastructure.
This works around the issue of Python lazily freeing resources.

girder/large_image,DigitalSlideArchive/large_image,girder/large_image,DigitalSlideArchive/large_image,girder/large_image,DigitalSlideArchive/large_image