[CI] Rolling upgrade tests (twoThirdsUpgradedTestRunner) fails

[pugnascotia]

Failure in CI, caused by an NPE:

• https://gradle-enterprise.elastic.co/s/mj7num4r7elh2

Two local failures while trying to reproduce: "timed out waiting for green state for index":

• https://gradle-enterprise.elastic.co/s/ub2df4zybdzui
• https://gradle-enterprise.elastic.co/s/fjnuzf5pmtfca

[elasticmachine]

Pinging @elastic/es-distributed (:Distributed/Distributed)