[CI] ThreadPoolMergeExecutorServiceDiskSpaceTests class failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #8955 / openjdk17_checkpart1_java-fips-matrix
• elasticsearch-periodic-platform-support #8970 / ubuntu-2404_platform-support-unix
• elasticsearch-pull-request #77461 / part-1
• elasticsearch-periodic-platform-support #8963 / amazonlinux-2_platform-support-aws
• elasticsearch-periodic-platform-support #8963 / rhel-7_platform-support-unix
• elasticsearch-pull-request #77321 / part-1
• elasticsearch-periodic-platform-support #8956 / oraclelinux-8_platform-support-unix
• elasticsearch-pull-request #77307 / part-1
• elasticsearch-periodic #8935 / single-processor-node-tests
• elasticsearch-periodic-platform-support #8950 / ubuntu-2004_platform-support-unix

Reproduction Line:

./gradlew ":server:test" --tests "org.elasticsearch.index.engine.ThreadPoolMergeExecutorServiceDiskSpaceTests.testUnavailableBudgetBlocksNewMergeTasksFromStartingExecution" -Dtests.seed=A04FD9D51F9FC63F -Dtests.locale=en-TO -Dtests.timezone=Australia/Lindeman -Druntime.java=17 -Dtests.fips.enabled=true

Applicable branches:
8.19

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

org.mockito.exceptions.verification.NeverWantedButInvoked: 
mergeTask.schedule();
Never wanted here:
-> at org.elasticsearch.index.engine.ThreadPoolMergeExecutorServiceDiskSpaceTests.lambda$testUnavailableBudgetBlocksNewMergeTasksFromStartingExecution$39(ThreadPoolMergeExecutorServiceDiskSpaceTests.java:871)
But invoked here:
-> at org.elasticsearch.index.engine.ThreadPoolMergeExecutorService.lambda$enqueueMergeTaskExecution$11(ThreadPoolMergeExecutorService.java:329) with arguments: []

Issue Reasons:

• [8.19] 2 consecutive failures in class org.elasticsearch.index.engine.ThreadPoolMergeExecutorServiceDiskSpaceTests
• [8.19] 249 failures in class org.elasticsearch.index.engine.ThreadPoolMergeExecutorServiceDiskSpaceTests (27.4% fail rate in 908 executions)
• [8.19] 5 failures in step openjdk17_checkpart1_java-fips-matrix (23.8% fail rate in 21 executions)
• [8.19] 8 failures in step ubuntu-2404_platform-support-unix (38.1% fail rate in 21 executions)
• [8.19] 39 failures in step part-1 (33.1% fail rate in 118 executions)
• [8.19] 12 failures in step part1 (16.4% fail rate in 73 executions)
• [8.19] 4 failures in step concurrent-search-tests (20.0% fail rate in 20 executions)
• [8.19] 7 failures in step single-processor-node-tests (35.0% fail rate in 20 executions)
• [8.19] 4 failures in step ubuntu-1804_platform-support-unix (20.0% fail rate in 20 executions)
• [8.19] 7 failures in step rocky-9_platform-support-unix (35.0% fail rate in 20 executions)
• [8.19] 5 failures in step almalinux-9_platform-support-unix (25.0% fail rate in 20 executions)
• [8.19] 4 failures in step oraclelinux-9_platform-support-unix (20.0% fail rate in 20 executions)
• [8.19] 5 failures in step ubuntu-2004_platform-support-unix (27.8% fail rate in 18 executions)
• [8.19] 2 failures in step ubuntu-2204_platform-support-unix (11.1% fail rate in 18 executions)
• [8.19] 4 failures in step oraclelinux-8_platform-support-unix (20.0% fail rate in 20 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

Pinging @elastic/es-distributed-indexing (Team:Distributed Indexing)

[albertzaharovits]

Closing this and will look into the individual test failures (the test suite class should now be OK).