[crosperf] Fix status reporting for multiple iters inside a single run.

If a single benchmark run contains multiple iterations (like
BootPerfServer), then only the first internal iteration was getting the
correct pass/fail status, so even though everything passed the report
title would claim 1 pass and 9 fails (for 10 internal iterations).
This fixes that.

BUG=chromium:426960
TEST=Ran BootPerfServer with change. Now shows correct number of
passes/fails for the iterations.

Change-Id: I9638b39c94692fd754698e64d89cb22c10e9d479
Reviewed-on: https://chromium-review.googlesource.com/470547


Commit-Ready: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
Reviewed-by: Yunlian Jiang <yunlian@chromium.org>