[Autotest] Fix bug in lock interval function

Previously there was a key error. entry['fields']['status'] does not exist.
Instead, it should be entry['fields']['locked'].

BUG=None
TEST=python host_history.py --index=cautotest --start="2014-08-12 00:00:00" \
                            --end="2014-08-13 00:00:00" --board=falco

Change-Id: Ib9da1dde83494af27a842590abd7fc958e3916eb
Reviewed-on: https://chromium-review.googlesource.com/212302
Tested-by: Michael Liang <michaelliang@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Michael Liang <michaelliang@chromium.org>
1 file changed