SERVER-66078 added an extra step to the lazy initialisation of the config.system.sessions collection performed by SessionsCollectionConfigServer to also persist a custom value for its max chunk size. As any write operation, such extra step should only be performed when running process acts as the primary node of the CSRS.

Nevertheless, there is no condition in place to prevent the new logic from also being executed by secondary nodes - and raising a PrimarySteppedDown error when a write is attempted.

This is causing the periodic refresh of the logical session caches in the CSRS secondary nodes to fail on each iteration when setupSessionsCollection() is invoked.