Ensure that TTL indexes work correctly with user write blocking

When user write blocking is enabled, we must not perform TTL monitoring/reaping on user data. However, reaping of system and internal collections must work normally.

There is no need to synchronize activation of user write blocking mode with the TTL monitor thread.

We should ensure that the TTL monitor thread, and the operations it issues, are affected by write blocking mode. We should write JS integration tests to validate that TTL indexes are disabled on user collections, and functioning on administrative collections.

A collection needs to be on one of the following databases to be considered administrative:

• admin
• local
• config

system. collections should not necessarily be considered administrative.