[autotest] Fix couple issues in host history from metadb

BUG=None
TEST=test against production db, unittest
./site_utils/host_history.py -l 24 --hosts chromeos4-row8-rack5-host17

Change-Id: Ib173671c4033e1a757009f5290c283eb4ea24643
Reviewed-on: https://chromium-review.googlesource.com/270790
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
2 files changed