Our lab testing shows that message loss is unacceptably high when using
presettled mode for non-trivial metrics volumes. "unsettled" mode (the
alternative) has been shown to be 100% reliable while still acheiving equal or
greater overall max throughput in live testing with a baremetal cloud.
Change-Id: I9388994ee94ab1e3c3e15768a8eb96069c2d8a0b
15dfacb655