Reduce kernel loglevel to 0

Change the kernel loglevel from 1 to 0 to avoid showing console
messages on the screen during shutdown.

An example is the "Power down." message that is shown when shutting
down. This appears on the screen because the kernel prints the
message with KERN_EMERG (level 0). As such, 0 < 1, and the message
appears on the screen.

BUG=chromium-os:28602
TEST=Tested on lumpy, saw no messages when shutting down.

Reviewed-on: https://gerrit.chromium.org/gerrit/22104
Reviewed-by: Olof Johansson <olofj@chromium.org>
Tested-by: Sean Paul <seanpaul@chromium.org>
Commit-Ready: Sean Paul <seanpaul@chromium.org>
(cherry picked from commit 078164ea8523906e19272e604be9586e892a4f12)

Change-Id: Id431f3b9ac87a4df7bcb6d8375a37e6f39fcf897
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/24999
Reviewed-by: Daniel Erat <derat@chromium.org>
diff --git a/build_kernel_image.sh b/build_kernel_image.sh
index d151da1..33bac8d 100755
--- a/build_kernel_image.sh
+++ b/build_kernel_image.sh
@@ -140,7 +140,7 @@
   cat <<EOF | cat - "${FLAGS_working_dir}/boot.config" \
     > "${FLAGS_working_dir}/config.txt"
 quiet
-loglevel=1
+loglevel=0
 console=tty2
 init=/sbin/init
 add_efi_memmap