We should create a full integration test of hot backups with ESE enabled, specifically testing that no KeyStore files are copied in $backupCursorExtend.

 
If a new database is created and a document is inserted into a collection while the $backupCursor is open, then when we open $backupCursorExtend with the operation time of the document insertion, we will not have to copy the KeyStore data for the new database. Instead, these operations will be stored in the oplog and will be replayed when starting up a node on the copied data files. The reason they are stored in the oplog is that these new operations are behind the 'checkpointTimestamp' returned from $backupCursor. During oplog recovery, the database will be assigned a new key in the KeyStore when its creation is replayed.