init: add FACTORY_RETURN_AFTER_WIPING flag in clobber-state

When in-place wiping we use FACTORY_RETURN_AFTER_WIPING to return to
original script after running clobber-state. Add this flag to enable
in-place wiping.

BUG=chromium:544021
TEST=Run in-place wipe auron-paine (6459)

Change-Id: I87623b7ab65fb175a0c3aac298558f8219d1178d
Reviewed-on: https://chromium-review.googlesource.com/309012
Reviewed-by: Bowgo Tsai <bowgotsai@chromium.org>
Commit-Queue: Shun-Hsing Ou <shunhsingou@chromium.org>
Tested-by: Shun-Hsing Ou <shunhsingou@chromium.org>
diff --git a/init/clobber-state b/init/clobber-state
index 6a54cfd..f88b5b6 100755
--- a/init/clobber-state
+++ b/init/clobber-state
@@ -312,6 +312,7 @@
 # board_factory_wipe.sh will be installed by the board overlay if necessary.
 if [ "$FACTORY_WIPE" = "factory" ]; then
   factory_wipe_firmware
+  [ -n "${FACTORY_RETURN_AFTER_WIPING}" ] && exit
   BOARD_WIPE=/usr/sbin/board_factory_wipe.sh
   if [ -x "${BOARD_WIPE}" ]; then
     ${BOARD_WIPE} ${WIPE_OPTION}