cfbot fails on v8 now and then. The stats test checks that blk_read_time grows after reading the table back, and that is not guaranteed.
The read time only counts how long the backend waits for a read. If the read is already done when the backend looks, nothing is added. pg_stat_database behaves the same way on master.
v9 drops that one check. No code changes. I also shortened the commit message.
