The metadata can potentially use such an event to clean up any
"unreachable" data, solving several problems we currently have
where obsolete data may continue to exist in the shared areas.
(Bitbake rev: c5e6f929f3d5eeb7954660dea62611c58b795ff8)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>