Leaving the savepoint in the transaction stack upon rollback is incorrect

• /core/lib/Drupal/Core/Database/Transaction/TransactionManagerBase.php
• /core/tests/Drupal/KernelTests/Core/Database/DriverSpecificTransactionTestBase.php

Closes #3407080

added 4 commits

• d73f9345...48b171f7 - 2 commits from branch project:11.x
• 9d04c0ef - Merge branch '11.x' into 3407080-leaving-the-savepoint
• aa41753d - add test for duplicate rollback

Compare with previous version

closed