build_image: remove use of cros_list_overlays

The list of overlays for the given board is set using
'/etc/make.conf.board_setup', which is already sourced in all the
build image scripts, so it is not necessary to use cros_list_overlays.

BUG=brillo:655
TEST=./build_image --board=panther --noenable_rootfs_verification test
TEST=brillo image --brick=//example-app/helloworld base

Change-Id: I6120d51f3df6dab34ba54741062250880a149e53
Reviewed-on: https://chromium-review.googlesource.com/262437
Tested-by: Steve Fung <stevefung@chromium.org>
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Steve Fung <stevefung@chromium.org>
diff --git a/common.sh b/common.sh
index 79a1afd..ee0722b 100644
--- a/common.sh
+++ b/common.sh
@@ -1034,9 +1034,9 @@
 # $1 - Board to match overlays to.
 # $2 - File to load.
 load_board_specific_script() {
-  local board=$1 file=$2 overlay
-  [[ $# -ne 2 ]] && die "load_board_specific_script requires exactly 2 params"
-  for overlay in $(cros_list_overlays --board "${board}"); do
+  local file=$1 overlay
+  [[ $# -ne 1 ]] && die "load_board_specific_script requires exactly 1 param"
+  for overlay in ${BOARD_OVERLAY}; do
     local setup_sh="${overlay}/scripts/${file}"
     if [[ -e ${setup_sh} ]]; then
       source "${setup_sh}"