A bit of history: in r71528, I tried to fix our explorer often
crashing while browsing directories. It was linked to the fact
that a notification result may arrive while the notification
structure had already been deleted.
The fix for this was actually broken and was leading to a double
leak: the notification structure was leaked. But also the handle
to the directory that had been browsed!
This means that the directory couldn't be modified anymore as
a leaked handle to it was still open.
Actually, when notifications are cancel, the kernel properly
calls the notification routine, but with a specific error code.
So the correct fix is to stop handling that notification when
we receive this error code. This is the correct fix with no leaks.
This commit is a complete r71528 revert with the appropriate fix.
CORE-10941
CORE-12843
