add "shutdown critical" to service

- "shutdown critical" prevents killing the service during
  shutdown. And the service will be started if not running.
- Without it, services will be killed by SIGTERM / SIGKILL during shutdown.
- Even services with "shutdown critical" will be killed if shutdown
  times out.
- Removes ueventd and vold from hard coded list. Each service's rc will
  be updated to add "shutdown critical". watchdogd is still kept in the list.

bug: 37626581
Test: reboot and check last kmsg

(cherry picked from commit cccb34fce8798f2a359c6eb0e394ef9460673629)

Change-Id: I3c6aeb7151e64beca4b435f843ae64455217262d
diff --git a/init/reboot.cpp b/init/reboot.cpp
index cdfc698..703e10b 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -331,13 +331,15 @@
     // keep debugging tools until non critical ones are all gone.
     const std::set<std::string> kill_after_apps{"tombstoned", "logd", "adbd"};
     // watchdogd is a vendor specific component but should be alive to complete shutdown safely.
-    const std::set<std::string> to_starts{"watchdogd", "vold", "ueventd"};
+    const std::set<std::string> to_starts{"watchdogd"};
     ServiceManager::GetInstance().ForEachService([&kill_after_apps, &to_starts](Service* s) {
         if (kill_after_apps.count(s->name())) {
             s->SetShutdownCritical();
         } else if (to_starts.count(s->name())) {
             s->Start();
             s->SetShutdownCritical();
+        } else if (s->IsShutdownCritical()) {
+            s->Start();  // start shutdown critical service if not started
         }
     });