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/service.cpp b/init/service.cpp
index 1a6474b..401561a 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -487,6 +487,14 @@
     return true;
 }
 
+bool Service::ParseShutdown(const std::vector<std::string>& args, std::string* err) {
+    if (args[1] == "critical") {
+        flags_ |= SVC_SHUTDOWN_CRITICAL;
+        return true;
+    }
+    return false;
+}
+
 template <typename T>
 bool Service::AddDescriptor(const std::vector<std::string>& args, std::string* err) {
     int perm = args.size() > 3 ? std::strtoul(args[3].c_str(), 0, 8) : -1;
@@ -591,6 +599,7 @@
         {"namespace",   {1,     2,    &Service::ParseNamespace}},
         {"seclabel",    {1,     1,    &Service::ParseSeclabel}},
         {"setenv",      {2,     2,    &Service::ParseSetenv}},
+        {"shutdown",    {1,     1,    &Service::ParseShutdown}},
         {"socket",      {3,     6,    &Service::ParseSocket}},
         {"file",        {2,     2,    &Service::ParseFile}},
         {"user",        {1,     1,    &Service::ParseUser}},