Add `ensure` to Pipeline's close method

[TimWillard]

Description

Ensure that the parent's close method is called in the event of a failure during the final flush. Without this, the connection is never returned to the pool, which can lead to deadlocks if a pool limit is set.

Types of Changes

• Bug fix.

Testing

• [ ] I added tests for my changes.
• [ ] I tested my changes locally.
• [ ] I tested my changes in staging.
• [ ] I tested my changes in production.