Add flag for restricting downloads

This adds a flag that can be used to turn off the ability to download
and apply updates from the API.  This value applies to all future
update checks that the update_engine performs.  Changing this value
during an update check has no effect on the current update check.

Bug: 66016687
Test: unit-tests, manual OTA

Change-Id: I655adf23cae44c63079bfa9dc18ba8ca65d7a304
(cherry picked from commit e22f2ddfec92623d38efbf17c17917f68e52907a)
diff --git a/binder_service_brillo.cc b/binder_service_brillo.cc
index 74803c4..c57561c 100644
--- a/binder_service_brillo.cc
+++ b/binder_service_brillo.cc
@@ -58,6 +58,10 @@
   return ToStatus(&error);
 }
 
+Status BinderUpdateEngineBrilloService::SetUpdateAttemptFlags(int flags) {
+  return CallCommonHandler(&UpdateEngineService::SetUpdateAttemptFlags, flags);
+}
+
 Status BinderUpdateEngineBrilloService::AttemptUpdate(
     const String16& app_version, const String16& omaha_url, int flags) {
   return CallCommonHandler(&UpdateEngineService::AttemptUpdate,