`Task#stop` should not stop nested transient tasks.

[ioquatix]

In some cases, transient tasks are created with a parent which could be stopped. But the transient task can outlive this parent task.

There are a couple of options:

• Create the transient task at the same time as the connection pool is created.
• Don't stop transient tasks when the are a child of a task being stopped.
• Always create transient tasks at the top level.