init: report createProcessGroup failure.

Also directly kill the initial pid for safety, like other libprocessgroup
users.

Change-Id: Ib28936aea19cceaeaa54734759d5ae0c252c7905
diff --git a/init/service.h b/init/service.h
index dc14f9a..8b3a0ad 100644
--- a/init/service.h
+++ b/init/service.h
@@ -111,6 +111,7 @@
     void ZapStdio() const;
     void OpenConsole() const;
     void PublishSocket(const std::string& name, int fd) const;
+    void KillProcessGroup(int signal);
 
     bool HandleClass(const std::vector<std::string>& args, std::string* err);
     bool HandleConsole(const std::vector<std::string>& args, std::string* err);