[autotest] Only try to get repo from host attribute if not running in chroot

For test running in chroot using test_that, there is no point to get repo from
host attribute.

BUG=chromium:237512,chromium:479842
TEST=local test_that
test_that -b peppy chromeos1-dshi1.cros dummy_PassServer
confirm the log has no entry like:
FAILED RPC CALL: get_hosts {'hostname': 'chromeos1-dshi1.cros'}

also test scheduler and run a test with scheduler

Change-Id: I40c83b8dca1f16a10fe1df1989b93b21f52be2da
Reviewed-on: https://chromium-review.googlesource.com/269784
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Mungyung Ryu <mkryu@google.com>
Commit-Queue: Dan Shi <dshi@chromium.org>
2 files changed