dev: Add network connection check

.. so we print ip info / halt until a valid network connection is
established against caching services in the lab.

BUG=b:394416482
TEST=emerge + builders

Change-Id: Ia50546728e5aa86c8312e66a4f5653bfa64214c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/6261669
Tested-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Congbin Guo <guocb@chromium.org>
Auto-Submit: Jae Hoon Kim <kimjae@chromium.org>
1 file changed