When running wtperf by hand with any config file (that does not use tiered), a non-error message is printed out:

tiered_flush_work_wait: timed out after 30 seconds

This is coming from tiered/tiered_work.c:_wt_tiered_flush_work_wait. There is a bug in the conditional for the message. We should only print that message if the timeout was reached. Right now it is getting printed if there is no work to do.