This patch introduces centralized logic of selecting what dbroot is
accessible in PrimProc on what node. The logic is in OamCache for time
being and can be moved later.
With an API txn (and likely other scenarios) cleartablelock will roll
back the txn and lock but leave a stale txn pointer in the BRM. This
causes restart/shutdown to warn that transactions are still open.
This patch makes sure BRM removes the txn from the list.