[autotest] Change to read global_afe_hostname from different config key.

global_afe_hostname now is in [SERVER] section instead of [SHARD].

BUG=chromium:524678
TEST=None

Change-Id: Ic10e100925e99e2b062fde618e6489664322c201
Reviewed-on: https://chromium-review.googlesource.com/295687
Commit-Ready: Mungyung Ryu <mkryu@google.com>
Tested-by: Mungyung Ryu <mkryu@google.com>
Reviewed-by: Dan Shi <dshi@chromium.org>
1 file changed