update_engine: Add powerwash flag to update status

Add a powerwash flag to the update status which is set to true if and
only if a powerwash takes place. This will ensure that the user is
informed of a pending powerwash exactly when it is going to happen.

BUG=chromium:1070563
TEST=FEATURES=test emerge-amd64-generic update_engine
channel change and update on test device

Cq-Depend: chromium:2187671
Change-Id: I58314ecc7c9c2e64c906ef5b31cb780948196296
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2187672
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Tested-by: Miriam Polzer <mpolzer@google.com>
Commit-Queue: Miriam Polzer <mpolzer@google.com>
diff --git a/dbus_service.cc b/dbus_service.cc
index 46ac1d1..a282d1e 100644
--- a/dbus_service.cc
+++ b/dbus_service.cc
@@ -47,6 +47,8 @@
   out_status->set_is_enterprise_rollback(ue_status.is_enterprise_rollback);
   out_status->set_is_install(ue_status.is_install);
   out_status->set_eol_date(ue_status.eol_date);
+  out_status->set_will_powerwash_after_reboot(
+      ue_status.will_powerwash_after_reboot);
 }
 }  // namespace