Chromad: Show proper error for the network error

Shows network error message instead of an unknown error message

BUG=842619
TEST=manual

Change-Id: I5149fbed8282c44e9cf1960d3b4a6f013095f983
Reviewed-on: https://chromium-review.googlesource.com/1098693
Reviewed-by: Alexander Alekseev <alemate@chromium.org>
Commit-Queue: Roman Sorokin <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567185}
1 file changed