.OSD now deletes old OSD maps as expected
When new OSD maps are received, the OSD daemon marks the unused OSD maps as `stale` and deletes them to keep up with the changes. Previously, an attempt to delete stale OSD maps could fail for various reasons. As a consequence, certain OSD nodes were sometimes marked as `down` if it took too long to clean their OSD map caches when booting. With this update, the OSD daemon deletes old OSD maps as expected, thus fixing this bug.