[CI] UpgradeClusterClientYamlTestSuiteIT class failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-intake #29085 / 9.2.0_bwc-snapshots
• elasticsearch-intake #29081 / 9.2.0_bwc-snapshots
• elasticsearch-pull-request #94952 / 8.19.5_part_2_bwc-snapshots
• elasticsearch-pull-request #94931 / 8.19.5_part_2_bwc-snapshots

Reproduction Line:

./gradlew ":x-pack:qa:rolling-upgrade:v9.2.0#twoThirdsUpgradedTest" -Dtests.class="org.elasticsearch.upgrades.UpgradeClusterClientYamlTestSuiteIT" -Dtests.method="test {p0=mixed_cluster/80_transform_jobs_crud/Test GET, stop, start, old continuous transforms}" -Dtests.seed=4389970EFAEA39C8 -Dtests.bwc=true -Dtests.locale=lmo-IT -Dtests.timezone=Asia/Calcutta -Druntime.java=25

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Failure in test setup: Failed to initialize at least 3 watcher nodes

Issue Reasons:

• [main] 4 failures in class org.elasticsearch.upgrades.UpgradeClusterClientYamlTestSuiteIT (0.4% fail rate in 1000 executions)
• [main] 2 failures in step 9.2.0_bwc-snapshots (22.2% fail rate in 9 executions)
• [main] 2 failures in step 8.19.5_part_2_bwc-snapshots (8.0% fail rate in 25 executions)
• [main] 2 failures in pipeline elasticsearch-intake (22.2% fail rate in 9 executions)
• [main] 2 failures in pipeline elasticsearch-pull-request (5.9% fail rate in 34 executions)

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

[elasticsearchmachine]

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

[joshua-adams-1]

Assigning a medium risk since we currently have four other open rolling upgrade test failures:

• [CI] RollingUpgradeSearchableSnapshotIndexCompatibilityIT testSearchableSnapshotUpgrade {p0=[9.2.0, 9.2.0, 8.19.0]} failing #135249
• [CI] RollingUpgradeSearchableSnapshotIndexCompatibilityIT testMountSearchableSnapshot {p0=[9.2.0, 9.2.0, 8.19.0]} failing #135248
• [CI] RollingUpgradeSearchableSnapshotIndexCompatibilityIT testMountSearchableSnapshot {p0=[9.2.0, 9.2.0, 9.2.0]} failing #135151
• [CI] RollingUpgradeSearchableSnapshotIndexCompatibilityIT testSearchableSnapshotUpgrade {p0=[9.2.0, 9.2.0, 9.2.0]} failing #135150

[joshua-adams-1]

Likely caused by a faulty assertion in #134786. The problematic change was reverted in #135476