[TEST] adjust chunk size to create less but bigger files to trigger throtteling more reliably
[SNAPSHOT] Minor code cleanup
[TEST] Wait until warmer is registered when testing timeout
[TEST] Only reset test cluster if a test actually failed

Previously we resetted the test cluster for all subsequent tests
even though they didn't fail. This make suites like REST tests faster
and prevents crazy timeouts.

Closes #7775
Aggregations: Fix regression bug for the support of terms aggregation on the `_parent` field.