[CI] SpecificMasterNodesIT testElectOnlyBetweenMasterNodes failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #9381 / windows-2025_checkpart1_platform-support-windows
• elasticsearch-periodic-platform-support #9381 / almalinux-8_platform-support-unix

Reproduction Line:

gradlew ":server:internalClusterTest" --tests "org.elasticsearch.cluster.SpecificMasterNodesIT.testElectOnlyBetweenMasterNodes" -Dtests.seed=F2DD817D21053921 -Dtests.locale=en-BZ -Dtests.timezone=America/Cayman -Druntime.java=24

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Master is not stable but the method expects a stable master node

Issue Reasons:

• [main] 2 failures in test testElectOnlyBetweenMasterNodes (0.8% fail rate in 238 executions)

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

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[elasticsearchmachine]

Pinging @elastic/es-distributed-coordination (Team:Distributed Coordination)

[ywangd]

Fixed by #131399