Fix ImageCache deadlock when file handles are exhausted
Fix ImageCache deadlock when file handles are exhausted

micler/oiio,OpenImageIO/oiio,cwilling/oiio,scott-wilson/oiio,lgritz/oiio,scott-wilson/oiio,lgritz/oiio,sambler/oiio,OpenImageIO/oiio,jeremyselan/oiio,OpenImageIO/oiio,OpenImageIO/oiio,bdeluca/oiio,YangYangTL/oiio,cwilling/oiio,sambler/oiio,bdeluca/oiio,YangYangTL/oiio,jeremyselan/oiio,YangYangTL/oiio,scott-wilson/oiio,cwilling/oiio,lgritz/oiio,scott-wilson/oiio,micler/oiio,mcanthony/oiio,jeremyselan/oiio,cwilling/oiio,sambler/oiio,mcanthony/oiio,bdeluca/oiio,mcanthony/oiio,mcanthony/oiio,micler/oiio,lgritz/oiio,micler/oiio,YangYangTL/oiio,sambler/oiio,bdeluca/oiio