When we first go to boot up the syncer, when we're in the active phase,
after we do the historical sync, we'll send a timestamp message that we
want everything, then transition to the passive mode. The test didn't
account for this extra message before, as the last test was being
re-used here (ran in parallel).
We fix this by asserting that the first expected message is sent, then
also the follow up messages as well.