This method is called to remove the given transaction from the transaction table/log.
Used to let the store remove all record from log and transaction table of the given transaction. This should only be used to clean up heuristically completed transactions, otherwise commit or abort should be used to act on other transactions.
If forget() is called on a transaction which has not be heuristically completed then it will throw an exception: SQLState.STORE_XA_PROTOCOL_VIOLATION.
@param cm The ContextManager returned from the find() call.
@param xid A global transaction identifier.
@exception StandardException Standard exception policy.