Measure the random IOPS of the replication-manager host's storage with sysbench

Runs the embedded sysbench fileio (2G of files, 16 KiB random read/write, direct IO, 16 threads, 20 s) in the working directory at the lowest CPU priority, then removes the files. Answers the host IOPS and that figure times the agents and, with apply=true, writes the latter to resource-manager-infra-iops. Representative when every node has the same storage.