[7.x] Improves flushing of application/container

[Firtzberg]

Reduces memory usage in (my) tests by several percent.

[driesvints]

@Firtzberg can you provide some benchmarks for this?

[taylorotwell]

Performance PRs aren't accepted without benchmark comparisons.

[Firtzberg]

@taylorotwell Consider it code cleanup then.
There are no details on how to make benchmark comparisons in the contributing guide.