Currently bool is used to check if scan node is active or not, and
if it is active the deletion can happen. Now if two thread tries to
delete the same node at same time, the first one to get the node
will delete the node and set the active bool to false. If the
delete operation leads to node being freed, the 2nd thread when gets
the lock tries to check the bool, if node is active and then return
if node is not active.
Now if before the 2nd thread check the bool, the memory is reallocate
and the byte pointing to the bool is overwritten with non-zero value
the 2nd thread will assume that node is still active and try to delete
and access an already freed node.
To fix this use cookie instead of bool to check if scan node is active.
Change-Id: Id6b9dc9d0ff8f091eef0bd648abc9d3198c3ad4b
CRs-Fixed: 2219667
c176a5241b