There are some paths in TTL that require specific timing conditions to be tested, we need to examine these and see what's feasible and add tests as appropriate.

• index not found in getValidTTLIndex called from _deleteExpiredWithIndex
  • index needs to be deleted before we get here,
  • but after doTTLIndexDelete in a non-clustered collection
• part of replset, not readable
  • beginning of _doTTLSubPass
  • we are during initial sync
  • should skip
• doTTLIndexDelete
  • collection has already been dropped by the time we get here