From WT-4571, this change newly added is_allocating variable to txn_state which maintains the global transaction table. That change requires any thread who tries to read this global txn_state to check until is_allocating flag is set to false (i.e., until the transaction ID becomes valid). This re-checking routine is already done in __wt_txn_get_snapshot and __txn_oldest_id_scan code and this ticket is to add this kind of routine to __wt_verbose_dump_txn.