As shown in BF-25087, the js tests that use the InternalTransactionChunkMigrationTest and RetryableInternalTransactionTest fixtures can sometimes get LockTimeout errors (for the config database) when trying to commit internal transactions. These timeout errors are rare but unavoidable. The two fixtures should be modified to retry internal transactions upon LockTimeout errors just like how the transaction API and the InternalTransactionReshardingTest retry internal transactions upon transient errors.