update_engine: Fix update check error crash

In commit 6bb001ff0c2a6b0f26e50354e6a53cd37eb780d4, the return value of
AttemptUpdateWithFlags() became dependent on the out_result of AttemptUpdate()
which is wrong. This dependency causes the error pointer not be populated when
the update check is failed/ignored. And historically, failure of the update
check does not mean the failure of the dbus signal.

BUG=chromium:848486
TEST=cros flash followed by an interactive update did not crash the update engine.

Change-Id: I440c51683bdfc9d671c38142c965466815c69f47
Reviewed-on: https://chromium-review.googlesource.com/1082979
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Nicolas Norvez <norvez@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/dbus_service.cc b/dbus_service.cc
index bb4ff33..c7bc9f0 100644
--- a/dbus_service.cc
+++ b/dbus_service.cc
@@ -50,14 +50,11 @@
   bool interactive = !(flags & update_engine::kAttemptUpdateFlagNonInteractive);
   bool result;
   return common_->AttemptUpdate(
-             error,
-             in_app_version,
-             in_omaha_url,
-             interactive
-                 ? 0
-                 : update_engine::UpdateAttemptFlags::kFlagNonInteractive,
-             &result) &&
-         result;
+      error,
+      in_app_version,
+      in_omaha_url,
+      interactive ? 0 : update_engine::UpdateAttemptFlags::kFlagNonInteractive,
+      &result);
 }
 
 bool DBusUpdateEngineService::AttemptRollback(ErrorPtr* error,