Use java.lang.ref.Cleaner for ClientBackedTransaction
Improve temporary file clean up by using a Cleaner to dispatch
cleaning tasks. Since it gives us a Cleanable, we can dispense with
a tracking map and removal from it -- Cleanable makes sure it is
called exactly once.
JIRA: CONTROLLER-1911
Change-Id: I02d2ee57a9fada2c54ba06008b6c28681a709748
Signed-off-by: tadei.bilan <tadei.bilan@pantheon.tech>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit
b0ea37067f7ac8d03cb785ce70616fa16a5ba5a4)