Currently all background tasks that ever acquire the global lock in any mode conflict with secondary application due to the PBWM lock. SERVER-26005 will make the FTDC thread not conflict. We should also audit all other background jobs and decide which ones should be able to run concurrently with a replication batch. For example, the ClientCursorMonitor thread should be able to run concurrently with replication, but the readConcern=majority SnapshotThread should not.